Whats the deal with lane minions?

So I used to play this game a ton. But I've taken off for about a 1 year or more. It seems like lane minions act differently? I have played a few games recently, with Irelia and Teemo top. Irelia was vs a Ryze, and Teemo was vs a melee.

When ryze cast spells at me, and im on top of him, and hes on top of my minions, they don't aggro him. But if the roles are reversed, and I do the same to him, his minions aggro me.

Is it 100% based on auto attacks??

As teemo, if I auto and im far away, but hes on his minions, they will chase me pretty much all the way to my tower? Even if the melee dives into me, and i attack and kite backwards, rarely if ever do my lane minions aggro to the enemy champ (if they are melee).