It means a past habit which doesn't exist now. "I used to smoke." = I did this as a habit in the past, but not any more.

Something used to happen= it happened regularly in the past, but no long happens. I find a lot of students become confused with these two phrases "I used to do" and "I am used to doing". The structure and meanings are different. For example: I used to live alone. (= I lived alone in the past, but I no longer live alone.) I am used to living alone. (= I live alone, and I don't find it strange or difficult because I've been living alone for some time.) I thought I would mention this point. I hope this information is helpful for you.

Another meaning relates to familiarity or expectation: "I am used to shoveling snow in the winter" means that I am familiar with shoveling, or normally expect to shovel snow in the winter."