Returning Player; need help adjusting.

I've always enjoyed the game, but for scheduling reasons, being able to play it has been difficult. I'm recently trying to get back into it, and a lot has changed. I went into a quick match of unranked PvP, and it seemed the players were expected to know a lot of things. In example, in the champion select portion, a Jax had teleport, and was yelled at by a Teemo who had claimed top lane. Is there any place I can learn or read up on these things, or any ways I can better fit in with the new community? Any things I should expect from players, or be expected to know/do? I'm not a bad player, a tad rusty, perhaps, but this new system (?) is definitely throwing me off a bit.