The game's platforming mechanics are very similar to most other Kirby games, as is Kirby's skillset. Kirby is able to jump, duck, slide, fly (by inflating himself), as well as perform his signature move: inhaling enemies. When Kirby inhales an enemy, it can be spit back out as a projectile, or swallowed. Normally this has no effect on Kirby, although specific enemies grant Kirby copy abilities, a staple of the Kirby games. Copy abilities replace Kirby's standard inhaling move with a special attack, depending on the enemy Kirby ate. For example, swallowing a fire-based enemy allows Kirby to become a fireball.
Kirby gets a ride with Coo the owl.
At any time during play, Kirby can summon Gooey—a blue, long-tongued blob first seen in Dream Land 2. Doing so costs Kirby two hit points. When controlled by the computer, Gooey follows Kirby around and helps him to defeat enemies. (Gooey can also be controlled by a second human player.) Gooey's abilities are similar to Kirby's: He can swallow enemies using his long tongue, then either spit them out or copy their abilities to a limited extent. Kirby can also inhale Gooey and swallow him, reclaiming his two hit points.
In addition to Gooey, Kirby can team up with any one of his six other friends, three of which were introduced in the previous game in the series. This friend mechanic allows Kirby to be ridden, carried or rolled, enabling new team-based abilities, as well as variations of Kirby's copy abilities.
Source: Wikipedia, Kirby's Dream Land 3 , available under the CC-BY-SA License.