Raspberry Pi Pico is a low-cost, high-performance microcontroller board with flexible digital interfaces. It incorporates Raspberry Pi's own RP2040 microcontroller chip, with dual-core Arm Cortex M0+ processor running up to 133 MHz, embedded 264KB of SRAM and 2MB of on-board Flash memory, as well as 26x multi-function GPIO pins.
For software development, either Raspberry Pi's C/C++ SDK, or the MicroPython is available. There're also complete development resources and tutorials to help you get started easily, and integrate it into end products quickly.
Detailed information in the Raspberry Pi Pico Wiki