when looking for injectors i notice some cars say "peak and hold" others say "saturated" ...... what do these terms mean?

 

It refers to the way they're activated, kinda. The P&H injectors need a resistor box, because they use high current coils, and will fry an ECU without the extra resistance. The Saturated injectors are direct-drive because they use a higher impedance coil. Saturated injectors can also puls a leeeeetle bit faster because of their electromechanical design (this is a rule of thumb, not an absolute).

 

Saturated injectors are high impedance and P&H are low impedance injectors. P&H will draw ~4A from the stock driver w/o a resistor pack. This will fry the driver which is made for saturated injectors which are made to handle only ~1A of current. Hence the need for the resistor pack to make it 'look' like a saturated injector.