Terraria is a 2D sandbox survival game. The gameplay is centered around exploring a randomly generated world while building structures, equipment, and weapons from gathered resources.
Pro Fun combat
It starts out simple, with you whacking away at slow moving zombies and flying eyes, gradually shifting to more fierce and fearsome enemies such as flying demons, agile lizardmen, and many more. To survive you'll have to be always on the move, dodge enemy attacks, and be accurate when you retaliate.
There are also plenty of weapons to choose from. Melee weapons such as swords, hammers, lances, and flails. Ranged weapons such as bows, crossbows, rifles, and miniguns. And various items that allow you to cast spells. Whatever you choose, it feels great to destroy hordes of enemies.
Pro Intriguing world
Terraria uses a bright color palette and an upbeat chiptune soundtrack to ease you into its world. However, once you start exploring and spend time in it you'll notice it's not as cozy as it first seemed to be. Blood Moons that rouse the dead from their graves. Goblin armies trying to destroy everything in their wake. Vast and dark cave systems, filled with odd creatures and various dangers. Ancient ruins, teeming with the restless dead and evil spirits. Pockets of decaying land, thriving with misshapen monstrosities. It's really fun to explore and discover something new about the world of Terraria.
Pro Lots of community servers, tutorials, and streams
Terraria has a large community of players on every platform including mobile, desktop, and console. Because of this, there are many servers to play on, as well as tutorials and Let's Plays. Finding content or help getting started is quite easy.
Pro Allows for freedom of expression for all ages, all at your own pace
Terraria has all kinds of tools and materials you can use to build whatever you can imagine. From housing, to furniture, to weapons, to types of structure, the possibilities are almost endless. This is great for children who enjoy building and problem solving, and for adults who enjoy the same. It also makes for a great objective-less game, where you can do just about anything you want at your own pace.
Con Low replay value for those who play it as an adventure game
Terraria is a sandbox platform-adventure game, so it partly hinges on beating various bosses. If you play it purely for the sake of defeating all the bosses, you might have little else to do afterwards. Restarting the game won't be as enjoyable either because you'll already know what to expect, causing continued play without a new goal feel mundane or boring.