In maryland you can have your permit for 18 months while your parents teach you to drive and you go to driving school (required) you must have (i think) 60 hours of approved documented driving hours on the road. This is described in your drivers ed. book you got at the MVA when you got your learners. You do not need insurance to drive a car in maryland with your permit, the car does need to be insured however. If it is your mothers car then she must have insurance on the car. She must also be with you when you are driving it while you only have a permit.
You cannot drive without a licensed driver over the age of 21 in the car with you while you have a permit. Don't try it!
Source,
Me i'm 18 living in maryland and have been driving on my permit for about 2 years now (just got my learner re-done today)