An endpoint is a digital twin that you created for your device in Kaa. An active endpoint is the one actively communicating data with / from Kaa in a billing cycle. When you have an endpoint in a platform, but no data exchange related to that endpoint occurs, the endpoint is not considered active.
That said, it is up to you what part of your device you want to call an endpoint. For example, you may create one endpoint for your smart fridge or split it into several - one for a freezer, one for a lighting unit, etc. Or, maybe, what you need is an endpoint representing an entire kitchen because you only need to measure total electricity consumption by all the appliances located there. Our pricing policiy, thus, is based on the number of active endpoints currently used by your Kaa account.