Just started learning python - question about types of statements. - eviltoast

Just started as in, I’m about an hour into a 4 hour intro video. Seeing two basic ways of manipulating things and don’t understand the difference.

If I want to know the length of a string and I just guess at how to do it I would try one of these two things,

  1. Len(string)
  2. string.len()

What is the difference between these types of statements? How do I think about this to know which one I should expect to work?