I believe they were generally from colleges and schools and received development assistance from NASA. Each cubesat is a certain size, in the case of Artemis 1, they are "6U" or 6-units large. This seems to be a standard designation. The adapter ring that launches the cubesats is also interesting. Little chutes.

Those are big cubesats! 3U used to be the normal size for a serious mission (eg I know of a space telescope that fit in 3U), while 1U is a few sensors or a toy project. I'm glad NASA is taking them up.