Do you know how to work on cars?
No but I have a close friend who does
Have they ever helped you with your car if it's been broken?
Yes they have they are called auto mechanic (automotive technician in most of North America, car mechanic in British English, and motor mechanic in Australian 
That's good to know, thank you. I should learn how to work on my car more but all I can do is change the oil.
Wow, their main role is to diagnose the problem accurately and quickly.