Ignorant means lacking knowledge or information about something. If you're ignorant about how engines work, you simply haven't learned about them yet. A person might be ignorant of the rules of chess because they've never played, or ignorant of what happened in history class because they were absent that day.

The word describes a fixable situation: not knowing something. Everyone is ignorant about countless topics. A brilliant scientist might be ignorant about music theory. A talented musician might be ignorant about chemistry. Being ignorant just means you haven't learned that particular thing yet.

However, the word often carries a negative feeling, especially when someone chooses to stay ignorant. If you refuse to learn about something important, or if you make confident statements about topics you're actually ignorant about, that's when ignorance becomes a problem. There's a big difference between admitting “I'm ignorant about this subject” and acting like an expert when you're not.

The noun form is ignorance. People sometimes say “ignorance is bliss” to mean that not knowing about problems can feel more comfortable than facing them, though this usually isn't wise in the long run.