SUBST

Well, subst stands for "substitute". That means it can help you use one thing instead of another thing, kind of like if you don't have a toy car, you can use a block to pretend it's a car instead.

But subst is really for computer things. Let's say you have a big file on your computer that you use all the time, but it's hard to find because it's in a really long folder path. Subst can help you create a shortcut to that file, so instead of typing out the whole long path every time you want to use it, you can just use the shortcut instead.

It's like having a little helper who knows where everything is on your computer and can make it easier for you to find and use what you need.