I will say that, while the other comment comparing it to Minecraft isn’t wrong to do so, you shouldn’t go in expecting some 1:1, 2D Minecraft experience. Because while they have plenty of similar features, the core of each game is quite different. Minecraft for example is primarily a sandbox game, with lite survival elements sprinkled in. You’re mostly just there to build and farm and do whatever the hell you want, and the game doesn’t differ greatly between peaceful and hard. Terraria on the other hand is primarily an action game with some survival elements. Sure, you can build huge, beautiful cathedrals if you’d like, but unlike Minecraft that’s not really where the game shines at all. Terraria instead shines in it’s exploration (especially when you’re new to the game) and combat.

Edit: Oh also, unlike Minecraft, world difficulties change things drastically. Difficulty isn’t just a damage and health slider for enemies, instead it also modifies general enemy AI (in honestly annoying ways sometimes - looking at you lava slimes), and bosses all get major changes including new attack patterns. I’d stick with classic or journey mode at first, even if you normally tend to try harder difficulties when playing new games.