If i left an apple iphone charger plugged into a wall would it and how much energy would it draw?

Apple chargers don't, but most other brands do. The Apple charger draws 0.010W for 500ms when the phone is either disconnected or the charger is initially plugged in, then switches off when it detects no load. This is one of the reasons why Apple chargers cost more.

A phone charger is basically a transformer. A transformer has two coils of wire, the primary and secondary coils.

So you know how AC works, right? The current flows in one direction, then it stops, then it flows in the other direction. It reverses 120 times a second. So instead of moving down a wire it sort of 'vibrates' back and forth.

The primary coil is hooked up across the 110v AC line. Each cycle of AC current builds up a magnetic field around the primary coil, which then collapses when the current reverses, and then the field builds up in the other direction. When there's a load attached to the secondary coil, the collapsing field induces a current in the secondary coil, which is what charges your phone.

But when there's nothing connected to the secondary coil, all the energy in the field goes back into the primary coil. Meaning no actual energy is taken from the current except for 'losses' caused by the resistance of the wire in the coil. I'm not sure how much these losses are but they're probably on the order of a milliwatt or two. (You could calculate them if you wanted to go to that trouble).

So a coil just left plugged into the wall will get slightly warm. It's using some power, but very little. Not enough to notice on your electricity bill. maybe 10 cents a year. And it's not going to burn out because you left it plugged in.