D&D uses miniatures during combat. They're useful for knowing where things are in relation to each other, so that it's easier to tell if an enemy is in range of an attack, or if a spell can hit one enemy or two, etc… But there are actually two different ways to run combat.

Dungeons & Dragons is many things at once: an exercise in teamwork, a shared narrative, a math game, and an opportunity to show off cool, immersive props such as costumes, strong roleplaying, and most of all, the use of miniatures.

The Dungeons & Dragons Miniatures Game, commonly referred to as DDM, served as Wizards of the Coast's official line of miniature figures for the Dungeons & Dragons game beginning in 2003, following the cancellation of the previous Dungeons & Dragons-based miniatures game, Chainmail, in August 2002.

One of the best places to start your D&D miniatures collection is at your friendly local gaming store (FLGS). These small businesses are dedicated to tabletop gaming and often have a great selection of miniatures from various manufacturers, as well as starter sets and boosters for the current editions.