basically the esp is a soc with integrated wifi
you can use it similar as an arduino

just check our esp category to learn more https://forum.pimatic.org/category/24/esp8266

on my pimatic blog there are 2 examples how i use the esp8266, especially the wemos d1 mini
https://blog.pimatic.org/pool-pump-control-and-balcony-lights/
https://blog.pimatic.org/boring-sunday/

for pimatic there are 2 very fine esp integrations available.
the first one is especially developed by our member koffienl only for use with pimatic and is named ESPimatic
the other one is the well known espeasy firmware which has recently also a pimatic integration available.

feel free to test both and if you have questions don’t hesitate

Best thermostat