Other forms: oftener; oftens
Often means "frequently," like if you see your friends every day, you see each other often.
The adverb often can mean "in great quantities," like you often stop by the donut shop, you might be shocked to realize you've been there hundreds of times in the last few years. Often can also mean "in many cases or instances." When a student starts to study more and get more serious about learning, it often leads to better grades.