What do the icons in the device list mean?

[raintonr]

What do these icons mean?

[Garfonso]

I thought the icons used to have tooltips... (but IIRC they were not very helpful, if you don't know the concept behind type-detector and so on).

The icons show which other iobroker adapters or services support this kind of device. The first three icons are Alexa, Alisa, and Google -> that means, the iot adapter supports these devices for the mentioned services, and you can use iot to control the devices by voice (out of the box).
The fourth icon, the bluish one, means that the material adapter supports the device, and you can use the materail visualization to control it (out of the box).

In general "devices" are meant to help adapters like iot or visualizations to "understand" what the states are about and what to do with them. So the icons try to give a rough impression of what you can do with the device.