The Raspberry Pi Pico from is a powerful SOC (System On a Chip) which delivers a 130Mhz Dual Core ARM Cortex M0+ Processor, supporting 2x SPI, 2x I2C, 2x UART, 3x 12-bit ADC and 16x controllable PWM channels and more, all in an Arduino compatible chip.
There are a wide variety of modules and boards which are now available with an RP2040 on board, allowing you to select the most suitable base hardware for your project, to get you moving as quickly as possible.
There is also the brand new Raspberry Pi Pico W which comes with a Infineon CYW43439 WiFi chip on board, and this is supported in the RP2040 Board Package from Earle F. Philhower. III which is detailed below from version 2.3.0+ (the latest is always recommended).