If you're familiar with the ESP32, the ESP8266 is similar, but less capable and less expensive. As far as I know, the ESP8266 was designed and sold as a wifi add-on chip for a separate microcontroller, but then an SDK came out and some applications don't actually need a separate microcontroller.
Depends on your project if it will work, but I use them around the house to report on temperature and humidity, and I've got one setup on an arcade video converter that I was hoping I could get better output from (but it didn't really work).
