What does the engine symbol mean on the dashboard?

That is most likely the Check Engine Light. In most usual cases, it's just a faulty sensor you need to replace. Any dealer of your brand of vehicle has code readers for these lights and could tell you what sensor is faulty. Beware, they can be costly though. Anything computer is. I believe you would not pass inspection if this was not fixed. Now if the Service Vehicle Soon light came on, stop driving it, you'd have a major issue that could kill the engine.