Terraria released eight months before Minecraft came out of beta in March 2011, although by that point Minecraft was already becoming very popular . It was one of the first games to be compared to Minecraft by PC players.
The main difference between Terraria and Minecraft is that Terraria is a 2D game, and graphically it has more of a pixel art style. The similarities lie in the gameplay, as you explore procedurally-generated worlds, craft needed equipment, fight monsters in the night, and construct cool structures to act as safe areas. Unlike Minecraft you can get NPCs to live in your buildings, and you can then trade with them using coins gathered by killing monsters.
Terraria originally released on the PC, but also found its way to the majority of recent consoles and handheld systems, including mobile devices. It has sold very well, even with the similarities to Minecraft, and a new game called Terraria: Otherworld is planned to release in 2016.