When you have "hands-on experience", it means that you have done something directly, on your own. In American culture, having "hands-on experience" is usually respected and valued higher than understanding something in a more general way.

The adverb "real" is often included with the phrase "real hands-on experience". This just makes it sound even more hands-on.

You can use the phrase "hands-on experience" in all situations: casual, formal, written, spoken, etc.