Difference between that and which.

So I think I kind of understand what you're trying to ask. In the scenario "the bird that did this" or "the bird which did this", the first one would be right. But it still sounds a little off. Personally if I was writing in my book, I would do "the (insert description word) bird flew into the air, spreading out its magnificent wings." I wouldn't include a which, or a that.

When I use them:
Which: I use that when I'm asking a question that's kind of comparing two things. For example "which one should I get?" Or "which dog did you like the best?"
That: I use this when I'm talking about something. For example "remember that one girl." Or "Who is that?"

I hope this helped you guys! Happy writing!