A type system is a set of rules that assigns a type to various constructs in a programming language, such as variables, functions, and expressions. Types can indicate the kind of data a variable can hold, like integers, strings, or more complex structures. This helps prevent errors by ensuring that operations on data are appropriate for its type, enhancing code reliability and maintainability. There are two main categories of type systems: static typing and dynamic typing. In static typing, types are checked at compile time, while in dynamic typing, types are checked at runtime. Each approach has its advantages and trade-offs, influencing how developers write and debug code.