Another way a comma can clarify your meaning is the following:
Sometimes commas are used to set off non-essential information. By non-essential, I mean that if the words set off by commas were removed, your readers would still fully understand what you mean.
Here are two examples:
1. Let’s eat, Grandma. If you remove that comma, you are telling your readers that you are a cannibal. But it really isn’t necessary to add “Grandma” because you are obviously speaking directly to her. You are simply saying to her, “Let’s eat.”
2. My ex-husband, Igor, lives in a dungeon. By setting Igor’s name off in commas, you are telling your readers that your ex lives in a dungeon, but it isn’t essential they know his name is Igor. You can remove his name and your readers will still understand your meaning completely. However, if you remove those commas around his name (and leave his name in), you are implying that you have at least one other ex-husband whose name is not Igor and probably does not live in a dungeon.