Terraria is the latest in the recent swarm of Minecraft likes, or more correctly Minecraft inspired titles.
In many ways it is exactly like Minecraft in 2D and its feature list can read a lot like a similar list about Minecraft. Mining is a big part of the game with many locations only reachable through this method and the primary way of acquiescing building and crafting materials with many of the same blocks from Minecraft showing up here as well. Additionally, it has a similar mechanic for wood gathering, biome, and is set in a randomly generated world.
But when playing the game the experience is very different; For one there is way more content; With a wide variety of monsters, some very unique, and a similar selection of weapons, tools, biomes, and even bosses. This creates a whole lot to experience and even though I have been playing for dozens of hours already I have at most seen 3/4 of what there is to see (with a fast paced level of change), and probably far less.
Also while it is nice looking (and even better then Minecraft at bad visuals) it is no where near Minecraft generating great looking, breathtaking, visuals. So the drive to explore is completely different in the two games. In Minecraft you explore to see the beautiful landscape, to see something that no one has seen before, but also to find and collect minerals; While in Terraria you are exploring mostly for loot and the minerals are something you collect along the way more then anything else. Also the two worlds are arranged far differently with far more vertical space given to Terraria; While you can build a tower to the top of Minecraft or mine down to the bedrock in easily under an hour. in Terraria it is a whole other story with multiple biomes spanning this vertical distance with many different characteristics and taking extreme amounts of time to traverse let along mine or build to.
Anyways enough about its similarities or lack there of with Minecraft. Terraria is a absolute joy to play and the most fun I have had in a long time. I am absolutely hooked on this game and have had so much fun and inspiration to build creatively and for a purpose. I have already undertaken and finished two major building projects, a castle with a inner keep and outer walls both with parapets and arrow slits as well as the very necessarily vertical travel shaft all the way down to the underworld (about 2000 ft).