There are a Windbond flash onboard, pic is here: https://statics3.seeedstudio.com/product/2016-09/7.png

Some description above the pic:

          • The size of ESP-3212 Wifi module is 16mm x 24mm x 3m.

          • The ESP-3212 deploys 4MB SPI Flash with WSOP－8 package. It also uses 3DBi PCB antenna on board.

ESP3212 is an module, ESP32 is the chip.