I'm trying to remove some restrictions programmed into a game like Sims 3 but some features like age restriction are hard-coded in the game's code so I read some tutorials and I found out that it's something hard-coded in the game's programming. What does hard-code mean in programming?
Hard-coded withing programming means that the functionality can't be altered without changing the programs code.
Using age restriction as an example. This will have been done in such a way that the age required can only be changed by making a code change rather than it being configurable through a file that anyone could change.
This is not really a programming question. In the context of video games, many games have files or assets available for users to change. This is called modding the game. Some games encourage this for users to make their own content for the game, others do not, but mods do exist for many games, especially PC ones.
Hard coded in this sense means that the code that controls this feature is not available in files that you have available for to change. Usually this means that it is set in the binary executable file of the game, and there is no easy way to get to that code.