Can someone please explain to me as far as voice classification - What is second tenor?

[Marcus B]

I was informed by my vocal coach today that I am a second tenor(we practiced the Entire scale A - G). I am becoming comfortable with F the range - which I read the highest a male can naturally can go up to(which I didn't actually have a problem doing that note but F7 & F8 - I had to actually do at least twice but I got it) but can someone who knows about music, provide a detailed and comparable answer?! Thank You much