Question on Chess notation

I just joined but I'm stumped on a small detail in the chess language. Here's a direct quote from one of the lessons I'm taking for 'Punishing bad opening Moves'

"Interesting is that 3.Nxe5 can already be considered by White, instead of 3.Bc4."

I understand the abbreviations for the pieces, N=knight, K=king, Q=queen, and so on, and I understand pawns lack their own abbreviations, which is what e5 stands for. And yes i know x means capture. So Nxe5 means Knight captures pawn at the e5 square.
What I don't understand is the 3. before the Nxe5. At first i thought it meant the rank number that the knight piece was on which was indeed on rank 3 but immediately after you can see it talks about the Bishop on the c4 square, but in front of Bc4 was the same 3. which blows that idea to pieces.

(3.Bc4)

What do these 3.s mean if they're not talking about rank?

P.S. is there a way to showcase photos on here? It would be a lot easier to show instead of tell

It's simply the third move in a sequence of moves. For example, a game may begin as 1.e4 e5 2.Nf3 f6 and now 3.Nxe5 is a legitimate move, the best move in fact in this position.

The 3 just means that it was White's third move.

Eh, Crazychessplaya edged me out...