Any thoughts?

it might be hard to see that the c6 knight is defending something important because it is an empty square, but if you look closely you will notice that white can get his own knight there and win the queen so the c6 knight is guarding a crucial square. so in essence bb5 is trying to win material but not in a direct way attacking a loose piece, rather removing an important defender and only then trying to win material by a fork. it's a combination of different tactics. if perhaps you asked yourself what the other person is trying to do with his move bb5, you should be able to see the capture he can now do that he did not have before, and then you would have to investigate the consequences of bxc6.

i'm not saying this is an easy thing to do, but it can be drilled by consciously doing it whenever it is relevant until it becomes part of your normal thinking process.

i don't know if there's a theme devoted to tactics that have a preparatory move like this one, but just by solving different kinds of simple tactics puzzles you should eventually be able to encounter this type of theme.

I did it on the website and not in the app. It allows you to post games and you can add your thoughts. 

Here you go:

What is the time control here?