A hotspot is a small portable box (the size of a bank card reader) with a (rechargeable) battery and can therefore be taken anywhere. If you want to connect equipment to the hotspot, you can only do so via the Wifi network that is broadcast by the hotspot. The range of that Wifi network is about 15 meters. The hotspot is ideal for temporary use on, for example, a flexible office space. Or when you are temporarily without an internet connection and you only want to access the internet with a few people at a time. You can connect up to 8 users to 1 hotspot at the same time.
A router is more powerful than the hotspot in every respect: better antennas for 4G reception and a larger Wifi range (up to 100 meters). The router only works on 230V and has no battery. On the other hand, the router also has a few LAN ports. This means that equipment can be connected to the router not only via the Wifi network but also wired. This is useful, for example, if you want to connect a printer that can then be used by all users in the network. The router is particularly suitable for small business use and can be used for a longer period of time.