You can read the link above for a full run down of its features. Figure it’s a platform where you could build and experiment with DSP based reverbs, delays, filters, and other effects.
I have used Arduino but have not used Daisy Seed. At first look it seems there are several ways to go about programming and several community applications available to test it out.
The build process is easier than most pedals. The number of parts on the boards is minimal. The hardest part is getting the six pots and 4 switches aligned. I soldered the pots first by mounting them on the board, putting it all in the enclosure, tighten down the nuts and washers, then soldering. Then I took everything out put the switches on the board, put it all back in the box, added the nuts and washer, and soldered. Repeat for the LEDs. A little tedious but makes everything align correctly.