Did that shadow just move?
You character, Sam Fisher, is a special operatives agent and a member of an agency called Third Echelon. Right from the first mission in the game, the agency sends him out into "the field" well equipped. He has guns, can shoot or throw projectiles to distract or disable opponents, and carries an assortment of equipment for completing different tasks.
The controls for the game are well laid out and precise. If Sam can reach something, usually he can use it to manoeuvre around or assist him in the environment and toward achieving his goal. The on-screen cross-hairs are great for helping you determine where to aim in order to precisely hit a target. This can require some trial and error; the game does not take the effects of gravity into account, even though it is applied to the projectiles being used to hit the target.
Depending on how you play, you can pass through each area drawing the same amount of attention as a firework at a busy intersection or as the shadow of a leaf in the forest. However, sometimes the light meter, which indicates how visible you are to others, does not agree with how visible you are on the screen. While there are a few problems with visibility and detection in the game, this does not make the game unplayable. It encourages you to experiment and to figure out more creative ways of dealing with opponents and obstacles in these sections of the game.
In addition to not being captured or killed during a mission, some missions force you to play without being spotted or without killing anyone. This can be frustrating, requiring more trial and error, but the results are usually very rewarding. Other than these limitations, you can try to complete the game however you like. If the difficulty levels offered, the environment, or opponents' AI are not challenging enough for you, you can create and pursue your own goals, such as fastest play-through time, trying to interrogate and knock out every character you encounter while passing through undetected, or the lowest possible body count for each mission (no body count for the game being impossible because some missions force you to kill in order to complete that mission).
Pick up and play a copy of the original Splinter Cell. You can buy it for a few dollars and, even after over a decade since its original release, it is still a game that is well worth playing.