Vocal (singular) means that there’s a sample voice singing the words of the song along with the music. It’s a very raw “scratch track” and is here to help you learn the song!
Vocals (plural) means that there’s children’s or women’s voices pre-recorded singing the words of the song and you can play it while you (or your community or students) perform it and sing along.
Inst, short for instrumental, means that it’s music only and you (or your community or students) perform it and sing live.
The songs are categorized by what is assumed most people may use them for. Certainly you can use any track for any program. For example, Little Torah can be part of a Mommy & Me weekly routine, but also performed at a Hebrew School graduation and also daily in a preschool classroom.
Another example, Hiney Ma Tov can be for a shlucha/shliach big birthday, a women’s event, a challah bake, or bas mitzvah. So, please look through all the categories so you don't miss anything good!