Templates are a feature of some programming languages, such as C++, that allows you to write generic and reusable code. They enable you to create functions or classes that can work with different data types without having to rewrite the same code for each type.

Templates are particularly useful for implementing data structures and algorithms that can be used with any data type. When you instantiate a template with a specific type, the compiler generates code for that type, ensuring type safety and optimal performance.

In C++, you can define a template function or class using the "template" keyword, followed by a list of template parameters enclosed in angle brackets (< >). Here's a simple example of a template function that swaps two values of any type:

template<typename T>
void swap(T& a, T& b) {
  T temp = a;
  a = b;
  b = temp;
}

int main() {
  int x = 1, y = 2;
  swap(x, y); // Swaps two integers

  double a = 1.5, b = 2.5;
  swap(a, b); // Swaps two doubles
}