Differences:
- The second form will only compile with a C# 3 compiler or later
- The second form doesn't let any code (even in the same class) access the field directly, as the real field has an "unspeakable name"
The second version is what's known as an automatically implemented property (or "automatic property" for short). They were introduced in C# 3. If you're only writing code which looks like the first version - i.e. there's no logic involved - then automatic properties are great. You can always add logic later by converting it into the first form. All your code will be compatible with that change, in both source and binary compatibility terms.
Be aware that in versions prior to C# 6, automatic properties don't allow you to specify default values, and there's no such thing as a genuinely readonly automatic property (i.e. one without a getter). The closest you can come is a public getter with a private setter, e.g.
public string Name { get; private set; }
It's not quite the same, but it's close enough in many situations.
