This contribution fund goes directly to progressive candidates who have endorsed Bernie Sanders.
You can see the list of candidates this fund currently supports directly to the right underneath the contribution amount. NOTE: You can also split your amounts there to give more to a candidate in your home state.
Candidates are liable to be added/removed based on future support with respect to Bernie and platform positions, but to the best of my knowledge, your contribution will always only go to the candidate specified at the time it was made.