The graphic below of a large, green circle with a brownish square in the center is what an actual cricket field looks like. In a two dimensional world with RGB colors assigned, anyway.
Seriously, though, this diagram shows a couple of important facts: Cricket fields are big circles and, in the center, where all the action is, there is a square where there's little or no grass.
You will notice the square in the center of the field is actually made up of several rectangular areas. That is because during a summer of playing, the brownish part where the bowling and batting take place--called the pitch--can get pretty worn out. So, there are several rectangular pitches that can possibly be prepared for use during the season. Just how all that happens isn't really important to us--at least, not right now. Later, when you're a real cricket nerd (or, as the Brits would call you, an "anorak"), we can get more into that stuff.
Here is a graphic of the pitch close up. Notice there is a set of stumps at each end, a batting crease at each end, a bowling crease at each end, and a return crease at each end. This is because the batsmen run back and forth to score runs, and because there are two bowlers taking turns from opposite ends every six balls.
The Batting Crease is what one might call "home" for the batsman. This is where s/he must safely arrive to score a run. If the ball is used to knock the bails off the top of the stumps while the batsman is out of the crease, then that batsman is out. The "Return" crease is where the batsman runs to. The Bowling Crease is where the bowler runs up to deliver the ball to the batsman.