Let's say I've got a copy on my server and a copy on my laptop. I fix a typo in the README on the server, as that's the window I've got in front of me. I push

Let's say I've got a copy on my server and a copy on my laptop. I fix a typo in the README on the server, as that's the window I've got in front of me. I push the change, but don't pull it onto my laptop. I don't pull the change to my laptop. I fix a different typo, and push it. I pull down the new version on the server. I fix another typo. Now this commit has two parents: the one from the server earlier, and the new one from my laptop. Because it has two parents, it's a merge commit.