You know it's never something I've thought about before but if a group of students came to me looking to go to a trade show I would expect them to use the word sponsorship, whereas if a homeless shelter came looking to support their daily operations, I would expect that to be a donation.

I think the critical different is that the sponsorship is for a specific activity, but I'm not sure.

There's certainly tax structure in place for donations in the US, but perhaps there is also a custom regarding sponsorship.