Can I create a shortcut to type a short sequence of characters?
You can do it from the substitutions list in System Prefs > Keyboard > Text, as in the example below.

The brackets are there in the example purely to make it file to the top [otherwise it gets mixed in with all my personal ones &amp; I'd have to blur them all out]

Just hit the + button at the bottom, type to enter your trigger, then double click in the result field &amp; type your desired output string. If you copy/paste into the output string, you can include carriage returns, for a full postal address etc, but you can't insert them manually.

Once setup, as soon as you hit the spacebar after a trigger keyword, it will auto-replace. Toggling 'correct spelling automatically' will change whether it suggests it to you before you've finished typing or not - as soon as it's recognised the correct replacement, space will trigger it, if 'auto' is on.

To avoid triggers which would otherwise be possibly confusing I always use ncsomething, historically because my originals used to be stored on NoteCards, but also now because I know of no word in English that starts with nc. So ncemail generates my email address, ncmobile for my phone number etc etc...  

I've found over the years that using a distinct word is easier to remember than a very short abbreviation, unless it's one you use a lot. 

As a bonus, you can also use it for spelling mistakes that aren't usually picked up by the normal spell-checker…
For example I frequently type pice instead of piece; for some reason spellcheck never picks that up so now it's in my substitutions list.
iCould is also one that gets past the checker, so I have one to fix that too, back to iCloud

Any changes you make to the substitutions list are 'live' immediately, you don't even need to close the window.