Inspired by this question: when should one play Bxc6, capturing the Knight, in Ruy Lopez?
Related, but hopefully not a duplicate: this question, but it focusses on why Bxc6 isn't a popular move, while I ask what factors and ideas to consider while making the move.
In the early stages of Ruy Lopez, Black's Knight is en prise for several moves and White's Bishop can capture it. However, this capture sometimes occurs and sometimes doesn't.
I haven't found a clear reason why White sometimes makes the capture and sometimes doesn't. It would help to know the what factors to consider before making the move.
I'd like to know the general ideas and motivating factors behind the capture (Bxc6), and when to, as well as when not to, make the capture (as White).