Jack of All Trades, Master of None

What does that even mean? No, I'm just kidding. It's a figure of speech quoted in a person who has a lot of skills but is not necessarily an expert in a certain field. Moreover, it's like a generalist rather than a specialist. So what does it even have to do with me? I have no idea. Someone just called me that while I was taking a short term course. The instructor asked some questions if we knew a little about it and I said yes. So, that's that. Here is picture of my dog.

Isn't he happy?