The “use” key, and how Half-Life used it well, and Bioshock Infinite used it poorly
The "use" key is probably something you're aware of if you grew up playing PC games, but the key's concept may be taken for granted by younger gamers. It's just a generic term for interaction, and it can do damn near anything you want it to, depending on the situation.
Which is kind of the problem. Interaction in games should be, at least ideally, meaningful. You should be able to impose your will on the game's world in satisfying ways. When it's used as a simple block, something you have to do in order to progress, it loses its power. If your only decision is either to press the button or turn the game off and go read a book, the use key loses much of its power and possibility.
This is an interesting look at the history of the "use" key, and how it's used well, and poorly, in games. Worth a read, especially if you're interested in the hows and whys of game design.