To fetch something is to go and get it. "Go fetch!" you might shout after your dog while throwing a stick into the yard.
Fetch comes from the Old English fatian meaning "grasp." When a dog fetches a bone, it grasps it in its mouth. You can ask your sister to fetch or grab your backpack off the table. If you sell something for a good price, you can fetch, or bring in, a decent amount of money. If you are sick of playing fetch, you might try to fetch a good price for your pooch.