I have heard that many people think that Terraria is basically a 2-dimension copy of Minecraft.
Terraria is a little inspired by Minecraft, and its created after Minecraft. However, there are some big differences between them.
First, Terraria is a 2-dimension game. Minecraft is a 3-dimension one. Terraria is a more fight-created game, and Minecraft is a more building game. A really big difference is that in Minecraft almost everything is made of cubes, while in Terraria that doesn't happen. Also, in Minecraft there aren't so much enemies in some categories, while in Terraria there are many enemies in every category. In Terraria there is no creative mode, no peaceful mode, and no chats in single player mode. Both are sandbox games, however Minecraft is mostly a building and survival game, with more things you must keep in mind to surive. In Terraria the game is less survival, without e.x. , the hunger meter that exists in Minecraft, but more a fighting and creating game.
I made a small blog for start, and I was having much more things in mind to write here and I have forgotten them...
P.S: If I have made mistakes in writing, I'm sorry. I'm not the best one in English!