"Pico" is sort of a nickname for the little RP2040 single board computer that you can buy for $4 these days. There is some confusion as to whether the "RP2040" refers to the chip or the little board.
This has a dual core ARM Cortex M0+ running at 133 Mhz, along with 264k of internal ram and 2M bytes of offboard flash. The board has a button labeled "bootsel" and the usual micro USB connector.
The board has 20 pads on each side and 3 pads on the end for a debug interface.
It has a permanent on board boot loader. To load firmware you hold down the boot button and keep holding it down while you plug in USB. It will then appear as a USB mass storage device. The file you drop in has the extension "uf2" and of course needs to be the proper format. Apparently any base name will work. Heaven knows what happens if several .uf2 files are on the device.
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