What does it mean that Christ is the "only begotten" Son of God?

Rob Ventura explains in this video that when Scripture describes Christ as the only begotten Son of God, it means that He is the unique Son of God. He is one of a kind. Christ is second person of the Trinity. This is what it means when Scripture talks about the "only begotten" Son of God. 

John 3:16 (NKJV) - "For God so loved the world that He gave His only begotten Son, that whoever believes in Him should not perish but have everlasting life."

Yes, when we talk about Christ as the only begotten Son of God, the Greek word menogeh, is really we're talking about him as the unique Son of God. In my Greek class we talk about John 3 16, God so loved the world that he gave his only begotten son, his unique son, his one of a kind son, because of course if we're born again we're all the children of God, but Christ in the Trinitarian sense, Christ as the Son of God, He is the unique only, a one-of-a-kind Son of God. He is the second person of the Trinity and this is what the only begotten Son of God refers to.