A field is a class-based variable that can be private to the class only depending on the access modifier that you use (e.g. public, protected, private).

A property on the other hand, has get and set methods and is used to access a field in a class.

public class ExClass
{
    //A field
    private string name;

    //A property
    public string NameProperty
    {
        get
        {
            return name;
        }
        set
        {
            name = value;
        }
    }

    //Shorthand for creating a property
    public string NameProperty2 {get; set;}
}