How does a vault contract work?

Hi! I was wondering how exactly does a vault contract work. Is it basically just an interface from where you call other contracts that are included in the strategy? A lot of the ones I’ve checked out looks surprisingly complex compared to when I’ve tried writing them myself. And are these vault contracts then called by an external js/python script running on a server? I’ve tried to read a lot of documentation provided by different farms/vaults but none seem to address how they are calling these contracts. If thats the case do the users just have to trust that one guy who is running server that he will maintain it?

I don’t know if this is the right subforum but feel free to move it if it doesn’t fit.

Thanks!