Right..... So you're saying that your code works? Like, it doesn't crash? That's... awesome...
Buzzword bingo does not add value. It only obscures meaning. Of course your code works. Of course you use existing technologies. That work. In existing code. That you leveraged. Using techniques. And technologies.
He was saying many other people have contributed java libraries his programs can use, so that he doesn't have to hire an expert in HTTP, or computational geometry, or many problem domains that aren't the direct concern of his application, yet are necessary for it to work.
He said it in a compact way. It's a form of compression.
Leverage = take advantage of
Proven = demonstrated to have worked
Techniques = using one approach versus another
Technologies = existing code