Commas (or as some confused people call them, "comas") are often thrown in by budding writers when they think a natural pause appears. It's like they want to mark a spot where the reader can take a breath if reading out loud. While it's certainly kind of them, it's unnecessary.
You may be asking, "Doug, can I use my commas in my cooking?"
"No," I answer, though I am interested in seeing you try.
You then ask, "Can I use them to stick together pieces of paper?"
"Not quite," I respond, "but you're getting closer."
Before you can even get a word out, however, I excitedly shout the answer, "YOU CAN PUT SENTENCES TOGETHER WITH THEM!!!" While you're recovering from my outburst, allow me to explain.
Compound sentences are essentially combinations of two sentences slapped together. One of the ways you can do so is with a comma and a connector. For example:
I lost the bet, so now I have to wear a dress.
The first sentence here is "I lost the bet," while the second one is "now I have to wear a dress." You'll notice there is also a "so" there. What of this "so"? It's our connector, a coordinating conjunction like for, and, nor, but, or, and yet. Add the "so" on the end there and you'll remember the words easily: "FANBOYS."
Now you're telling me, "But Doug, I know this already. It's kids stuff."
Slow down there, sport. I got something else to tell you. There's another way you can paste two sentences together and it's with a little something I (and most people) like to call a semi-colon. You've probably seen it before; you might see it in this sentence here. You'll recognize it as the little brother to the colon, like a colon with a tail, but truthfully the two punctuation marks are functionally dissimilar. Let's look at our earlier compound sentence:
I lost the bet; now I have to wear a dress.
It looks a little cleaner, doesn't it? No comma, but also no connector. Don't let the cleanliness fool you, however. If you use a semicolon too much, you may get semicolon-happy. Some people want to use a semicolon when they actually want to use a comma. Our EIU Writing Center Punctuation Pattern Sheet notes that it's "most effective when used sparingly." Too many semicolons can make your paper semigood.
It's important to remember that, though the semicolon looks like a comma with a great idea, they're not perfectly interchangeable. Think of the dot in the semicolon as compensating for the missing connector; if you don't have the dot, all you have is a comma. And then you just look ridiculous.