A check engine light is an indicator of something going wrong with either your vehicles engine, electrical system, catalytic converter or even as simple as a bad catalytic converter or a clogged catalytic converter.
A check engine light can sometimes mean something serious with your engine is going on while other times the check engine light may not be very serious at all.
If your check engine light is coming on then I would first check to make sure your gas cap is on all the way and tight and make sure the gas cap is good and is sealing properly.
Other times the check engine light can also be an indicator of something such as a misfire due to bad ignition coils, bad ignition module, bad spark plugs, bad spark plug wires, low fuel pressure etc.
When your check engine light comes on you can take your vehicle to a place such as Autozone or a mechanic and have them pull the codes from your vehicles computer.
Autozone will do it for free and sometimes an auto shop will do the test for free as well but some might charge a small fee.
The check engine light test will tell you exactly what is going on with your vehicle and why the check engine light is on.
Then when you know what is causing the problem for the check engine light to come on you can then fix the problem and the check engine light should go out.
If the check engine light stays on after 100 miles of driving then you might need to have the check engine light turned off by a mechanic.