MacOS – Are there any apps which will “watch” constantly and trigger actions when I type a certain string

Good sirs.
Coming from Windows-land, I'm trying to figure out what it is possible to do with my new laptop.

Using autohotkey (windows), I was able to open documents, launch apps, etc, by typing any pre-set combination of numbers and letters I could think of.
The keyboard hook was system-wide. I didn't have to open anything like spotlight, alfred, quicksilver, etc.

I could just type the word, no matter what app, and the script would run what it was told to.

I imagine that creating an OS which allowed this exploit would be frowned upon by the apple engineers, but all that aside, has anyone made an app that runs like this and constantly watches all key input?

Would learning applescript take care of something like this?

Thanks

P.S. I have also been trying to map spotlight to the esc key. But something has already claimed the esc key. Any ideas what that would be?