Turok is from a time when expectations towards an FPS were different. You play as Turok, a guy we know nothing about, aside from his uncanny ability to run at ludicrous speeds, and even faster when going diagonally. The only line ever uttered by the protagonist is "I AM TUROK!," and the game never goes beyond this state of mind. Not even an attempt at providing a story or purpose for what you're doing is made, and frankly, this is not to the game's detriment.
Turok scores where it really matters: the levels are vast and intricate, enemies plentiful, and the weapon roster is extensive to where you'll quickly run out of keys on your keyboard. Turok uses a hub-based level system, meaning you get to to travel to each level from a central hub, and in order to unlock new ones you need to collect keys. These are sometimes more and sometimes less well hidden, though the automap is quite helpful in finding one's way through the levels. Aside from shooting humaoids, dinosaurs, and alien creatures, one also gets to do a decent bit of platforming, which can be nerve-recking at times, albeit in a good way, as the game uses a checkpoint/save station system.
In terms of difficulty, the game is somewhat unbalanced. Normal can be beaten without any effort, to where losing health becomes harder than filling it up again. Hard on the other hand quickly becomes stressful, since several hitscan enemies can empty one's health bar in seconds, and once you run out of lives it's game over, not to mention that enemies respawn quickly while ammo does not. In addition, some mechanics such as maximum health increases are not present on hard difficulty at all, making things even trickier. Thankfully, the game allows changing the difficulty at any time, so one can start on hard and switch to normal during the tougher parts no problem.
The remaster by Nightdive is excellent as always. The original aesthetic is preserved, and the game runs great throughout. All in all, an easy recommendation.