Hi guys and girls just wondering can anyone tell what is lag and how does it affect the motor

Lag is when you slam your foot to the floor and nothing happens until the turbo spools up and starts to boost. That nothing happening is "lag".

Lag only happens with turbo'd cars. It's both annoying and fun, annoying because nothing happens when you want it to and fun because when it does happen it comes on with a bang!

Not to be confused with cut in speed. Below a certain rpm the turbo does nothing as flow through the turbine is insufficient. Once flow (rpm) picks up it can start working. This is often confused with lag. Lag is exactly what ssskiwi says, spool up time.