The tire is the only thing connecting your rig to the ground, so this choice matters. Shop everything in off-road tires.
All-Terrain (A/T)
The do-everything choice. A/Ts are quiet on the highway, grip well in rain and snow, last longer, and still handle dirt, gravel and moderate trails. If your truck is a daily driver that wheels on weekends, start here. Look at Toyo Open Country, Nitto and Falken.
Mud-Terrain (M/T)
Aggressive, self-cleaning tread for deep mud, rocks and sand. M/Ts trade some road manners and tread life for maximum bite. If you spend real time in technical terrain, they're worth it. See Mickey Thompson and Maxxis.
Reading a tire size
A size like 285/70R17 means 285mm wide, a sidewall 70% of that width, on a 17" wheel — roughly a 32.7" tall tire. Off-road sizes are often shown as 35x12.50R17 (35" tall, 12.5" wide, 17" wheel). Confirm clearance on your vehicle's page before you size up.