Feats

"A feat represents a talent or an area of expertise that gives a character special capabilities. It embodies training, experience, and abilities beyond what a class provides. At certain levels, your class gives you the Ability Score Improvement feature. Using the optional feats rule, you can forgo taking that feature to take a feat of your choice instead. You can take each feat only once, unless the feat’s description says otherwise. You must meet any prerequisite specified in a feat to take that feat. If you ever lose a feat’s prerequisite, you can’t use that feat until you regain the prerequisite. For example, the Grappler feat requires you to have a Strength of 13 or higher. If your Strength is reduced below 13 somehow—perhaps by a withering curse— you can’t benefit from the Grappler feat until your Strength is restored."- Feats, Dungeons and Dragons Player's Handbook 5th Edition

Grappler
Prerequisite: Strength 13 or higher You’ve developed the skills necessary to hold your own in close-­quarters grappling. You gain the following benefits:
 * You have advantage on attack rolls against a creature you are grappling.
 * You can use your action to try to pin a creature grappled by you. To do so, make another grapple check. If you succeed, you and the creature are both restrained until the grapple ends.