As usual, the official docs say it best :)
Take note of that fact: IF you want to learn something new then the official documentation usually has the best and most up to date tutorial. This isn’t always the case, but it’s always a great place to look.
Start here: https://www.typescriptlang.org/docs/handbook/basic-types.html Familiarise yourself with the entire handbook. Start from the top.
Since you are already a coder it should all feel very familiar.