Question: Is Nest considered a smart thermostats?

Nest Learning Thermostat



The Nest Learning Thermostat (or Nest Thermostat) is a smart thermostat developed by Nest Labs and designed by Tony Fadell, Ben Filson, and Fred Bould.[1] It is an electronic, programmable, and self-learning Wi-Fi-enabled thermostat that optimizes heating and cooling of homes and businesses to conserve energy.[2]
The device is based on a machine learning algorithm: for the first weeks users have to regulate the thermostat in order to provide the reference data set. The thermostat can then learn people's schedule, at which temperature they are used to and when.[3] Using built-in sensors and phones' locations, it can shift into energy saving mode when it realizes nobody is at home.[4][5]
Specifications - North American versions

Note: Generation E supports 2 stage cooling OR 2 stage heating OR heatpump due to a shared multi-use terminal.

Hardware
Nest is compatible with most standard HVAC systems that use central heating and cooling and uses industry standard connections to facilitate the control of these appliances.[6]
Nest is not compatible with communicating HVAC systems. Communicating systems are used with some two-stage and all variable-capacity HVAC systems. These systems require just four wires – two power wires for heating and cooling and two for communication between components (see photo). [7]

Nest consists of two primary pieces of hardware. The display contains the main printed circuit board (PCB) and rotating ring, and the base (pictured) houses the connection terminals, bubble level, and holes for wall anchors. Neither can function independently; if separated, the display becomes inactive until reconnected to the base.[8]
A special version of Nest is available in Europe, which is capable of controlling 230 volt heating systems. The Nest is paired with a "Heat Link" device, which contains the circuitry required for controlling the mains-voltage heating system.[9]  The first release was the 2nd Generation Nest thermostat which the Heat Link controlled the central heating boiler.[10]  The 3rd Generation added support for OpenTherm and for controlling domestic hot water.[11] The Nest E was made available to the UK in October of 2018.[12] It has several major changes as the thermostat is stand mounted only, the Heat Link is grey and battery powered, the Heat Link loses the domestic hot water support, and lastly designed to be installed on the wall where the old thermostat was located.[13]
The Nest Temperature Sensor was added in March, 2018.  Up to six of these battery operated devices can be added to a single thermostat to provide remote temperature monitoring.  Nest will then use the appropriate sensor based on schedule. Since they use Bluetooth Low Energy they are only compatible with the E and 3rd generation thermostats.[14]
Software

The Nest Thermostat is built around an operating system that allows interaction with the thermostat via spinning and clicking of its control wheel, which brings up option menus for switching from heating to cooling, access to device settings, energy history, and scheduling. Users can control Nest without a touch screen or other input device[15]
. As the thermostat is connected to the Internet, the company can push updates to fix bugs, improve performance and add additional features. For updates to occur automatically, the thermostat must be connected to Wi‑Fi and the battery must have at least a 3.7 V charge to give enough power to complete the download and installation of the update.[16]
The Nest Thermostat has had a number of software updates.[17] A recent security update enables two factor authentication.[18]
Many have commented on the company's "Nest Community" regarding the lack of prominent display of the current temperature.[16]
The operating system itself is based on Linux 2.6.37 and many other free software components.[19]
To comply with the terms of the GPLv3 license under which some components are available, Nest Labs also provides a special firmware image which will unlock the system so that it will accept arbitrary code sent to it.
While the thermostat software by Nest Labs itself remains proprietary, a third party has reimplemented the basic logic in an open source replacement called FreeAbode.

Nest devices interconnect with each other using a protocol called Weave, which is based on IEEE 802.15.4 and Wi-Fi 802.11 b/g/n.[20]
Availability
Nest is available for sale in the United States, Canada, Mexico, the United Kingdom, Belgium, France, Ireland, the Netherlands, Germany, Austria, Italy, and Spain.[21] It is, however, compatible with many heating and cooling automation systems in other countries.[22] Nest Labs have surveyed existing users known to be outside the areas where it is officially available. Use of the thermostat outside the United States and Canada is complicated by the software setting time and other functions based on the ZIP code. For international users this means they must either disable Wi‑Fi to set the time correctly or use the nearest U.S.zipcode which may result in erratic behavior as the thermostat makes faulty assumptions about inactivity corresponding with either sleep or the home's occupants being away.[23]
In 2013 a man-in-the-middle hack potentially allowed worldwide users to set up their timezone and local weather.[24]
Marketing
In an effort to increase the number of homes using their learning thermostats, Nest began to partner with energy companies. In February 2014, Direct Energy and Nest laboratories launched their Comfort and Control plan. The plan allowed Canadian customers in Alberta to receive a learning thermostat when they signed up for a five-year electricity contract.[25] In April 2014, Nest announced a partnership with the United Kingdom energy supplier nPower. The partnership offers customers a cut on the Nest installation price and locked energy prices for 5 years, when customers receive both gas and electricity from nPower and paying with direct debit.[26]
In June 2014, Direct Energy and Nest Laboratories expanded the package to Direct Energy's United States market.[27]
SKUs / Model numbers

T100577 is 1st Generation, released only in the US
T200377 is 2nd Generation, UK release
T200477 is 2nd Generation, Canada release
T200577 is 2nd Generation, US release
T200677 is 2nd Generation, France, Netherlands, and Belgium release
T3007ES is 3rd Generation, US release[28][29]
T3008US is 3rd Generation, US release, pro packaged
T3010FD is 3rd Generation, France release[30]
T3010GB is 3rd Generation, UK release[31][32]
T3016US is 3rd Generation - black ring, US release[33]
T3017US is 3rd Generation - white ring, US release
T3021US is 3rd Generation - copper ring, US release
T4000ES is Thermostat E, US release[34][35]
T4000EF is Thermostat E, Canada release
T5000SF is Temperature Sensor - white, US and Canada release
T200477 and T200577 are technically the same[36]

T200377 and T200677 are technically the same, except for the power plug used for the USB charger[37]