What is the difference between a {get; set;} property and a public variable?

Question

I’m programming in C# and I always see them use propriedades allowing to take and set the value of the variable, but what is the sense of this? When you let it just take the value or something I kind of understand, because it’s less work than creating a método to take this value, but when it is the simplest I do not understand. There is real difference between the two codes below?

public int Numero { get; set; }
public int numero;