git graph what do the lines and asteriks denote?

Trying to understand git in a bit more detail. In the graph output of git log, what do the lines and dots mean? Why are the dots only on the left for part of it, and only on the right for another part? Is it because I ran the command from a specific branch? Would it be different form master? Is a pull merge shown differently?

The asterisks denote commits and the lines parent child relations.

So basically it means that you have two branches (let's call them left and right). That you worked a lot on the left one, next on the right one, you merged the right in the left, worked further on the right one and merged again.

In case you do a merge they use some ASCII art to denote that the right one is still active. That's one of the reasons I prefer tig who has a cleaner syntax.