A tutor is someone who gives private instruction: tutors teach one-on-one.
If you ever helped someone learn something, you could say you tutored them. "Tutor" is also the title of someone who works with students one-on-one. There are writing tutors, music tutors, math tutors, and history tutors. You can find a tutor for just about anything you'd like to learn. Tutoring also sometimes means being the guardian for someone. In all cases, tutors tend to be helpful to their tutees: the people they tutor.