Or part of one, that is. There are a lot of ways to use commas, but I’m going to talk about just this one for now.
When writing about someone talking to another person, you put a comma right before you write that other person’s name. Example: “How are you today, Zeke?”
When you are telling another person about someone, you don’t use the comma. Example: “Did you hear what happened to Zeke?” Another example: “This is my brother Zeke.”
If you had written; “This is my brother, Zeke,” you would have indicated to your reader that you were speaking to Zeke. Any time you use a comma right before someone’s name, that tells your readers you are speaking to that person. When you don’t have a comma there, that means you are talking about that person.
A comma indicates a pause in the sentence. Whether people realize this or not, everyone does pause, a very brief moment anyway, right before they say the name of the person they are talking to. They don’t when they are talking about someone else. It’s an unconscious thing and you can notice it if you pay close enough attention. That’s why we use a comma in that manner when talking to or about people. Okay. Enough said.