Suggested datasheet-based description:
ESP-01S is an Ai-Thinker 802.11 b/g/n Wi-Fi module in a DIP-8 plug-in package, featuring an integrated Wi-Fi MAC/BB/RF/PA/LNA, low-power 32-bit CPU up to 160 MHz, UART/GPIO interface, onboard PCB antenna, default 8 Mbit SPI flash, AT command support, and STA/AP/STA+AP operating modes. It operates from 3.0–3.6 V with a supply current capability above 300 mA and supports low-power sleep modes for IoT networking applications.
Shorter version:
Ai-Thinker ESP-01S DIP-8 802.11 b/g/n Wi-Fi module with integrated RF front end, 32-bit CPU, UART/GPIO interface, PCB antenna, AT command support, and 3.0–3.6 V operation for IoT networking applications.