Generics are functions or types (classes) not caring what they work with. They let you write code that works for any type, without rewriting it for each one.

You can recognize a generic by the angle brackets syntax: <T>

A common use of generics is in collections like List<T> or Dictionary<TKey, TValue>.

Example - a stack

Here's a very basic implementation of a Stack.

public class Stack<T>
{
	private class Node<T>
	{
		public T Data { get; set; }
		public Node<T> Next { get; set; }
		
		public Node(T data, Node next)
		{
			Data = data;
			Next = next;
		}
	}
	
	private Node<T> top;
	
	public void Add(T data)
	{
		top = new Node(data, top);
	}
	
	public T Remove()
	{
		if (top == null)
			throw new InvalidOperationException("Stack is empty");
		
		T result = top.Data;
		top = top.Next;
		return result;
	}
}

public void Main()
{
	Stack<int> myStack = new Stack<int>();
	myStack.Add(1);
	myStack.Add(2);
	myStack.Add(3);
	myStack.Add(4);
	int x = myStack.Remove(); //4
	myStack.Add(5);
	//myStack will be [1, 2, 3, 5]
}