How do I create a group in Google Gmail?

Yes there is, and in the world of Google Gmail, it's a "group" that you want to create. To do so, start by logging in to your Gmail account, then click on the Contacts menu item on the left side of the page. It'll look roughly like this:

Now click on the Groups tab and you'll see:

As you can see, I don't yet have any groups. Since you're asking, you probably won't have any either. Click on Add a Group in the middle of the window and you'll get a blank group input form:

Type in the name of the group you'd like to create, then in the Add Contacts box, enter each of the members of your new group. When you're done, make sure you press "Create Group" to actually save your new group and you're done.

Now, the next time you're about to mail your group, type in the first few characters of the group name and you'll be delighted to see it pop up, ready to use!