The Atlantis takes it name from a mythological island on Earth that spawned an incredibly advanced culture in primitive times. The mythology states that the island was lost to the sea in a great cataclysm, and people for millennia after attempted to prove this island and culture even existed. Mostly, Atlantis represented what things could be like, and caused other cultures to strive for greatness too.
One of Starfleet's most advanced designs to date, the Intrepid-class Light Explorer comes equipped with a host of sophisticated technological advances designed to help it perform its mission, and to give it the effectiveness of ships much larger and less maneuverable than it. These include multi-spectral shields, bio-neural computers, special SIF reinforcement grids along the hull, an auxiliary deflector, and an advanced warp propulsion system (supplemented by a "spare" warp core, actually a sufficient collection of parts to build a replacement core if necessary).
The Intrepid can attain extremely high speeds not only because of its advanced warp core, but due to its variable geometry warp nacelles, which allow the ship to adjust its warp field for maximum efficiency. The vessel's streamlined shape also allows it to project an unusually efficient warp field. To ensure that the ship does not experience a catastrophic warp speed collision, it has two navigational deflectors - a main one on the forward end of the engineering hull, and a much smaller auxiliary deflector on the forward dorsal end of the saucer section.
The Intrepid's bridge module can separate from the main hull, and has its own maneuvering thrusters so that the crew can steer it. The detachable bridge has no weaponry.
Since the class' primary mission profiles involve exploration and scientific experimentation, it possesses an extensive complement of laboratories and scientific facilities. Each ship has two laboratory slots which are particularly advanced; Starfleet's engineers decide which labs to place in those slots (and thus which scientific tasks the ship excels at) when building each vessel. Most laboratories are on decks seven and eight.
The captain's yacht attached to the Intrepid is a special ship known as an "Aeroshuttle." Patterned in part after the Danube-class runabout, it is slightly larger and more maneuverable than a typical yacht.
Although not intended as a front-line combat vessel, the Intrepid has powerful tactical systems. These include multiple Type X phaser arrays and four high-yield torpedo launchers. The ship ordinarily carries Type II and Type VI torpedoes.
Most intriguingly of all, the Intrepid has atmospheric and planetfall capability - making it the largest Starfleet vessel with those abilities. When it lands, four large articulated "legs" emerge from the ventral side of the engineering hull to support it.