Mostly, for me, it comes down to union types, intersection types, the ability to disallow implicit nulls (meaning null must be declared as a valid value at the type level, and therefore cannot creep in unexpectedly), string literal types, discriminated unions (most of the good stuff from algebraic data types), and index types.

All demonstrated here: https://www.typescriptlang.org/docs/handbook/advanced-types....

The result is a very nice, expressive way to state your types and get maximal benefit from the type checker.