
Max M. answered 04/10/19
Harvard Literature major with 20 years of coaching writers
"I used to do something" means there was a time during which you did the thing with some regularity (i.e., more than once), and you are also implying that you no longer do it.
"In my childhood, I used to like chocolate milk and Frosted Flakes for breakfast."
The name for that tense is "imperfect," and it also covers "I was doing." It's the tense that describes continuous action in the past, as opposed to single past events, which use the simple past.
"I used to like [imperfect] chocolate milk, but then I suddenly realized [simple past] it was unhealthy."
If you want to think of the "tool" idea that was in your question, you can think of the "to" form of the verb (the infinitive, if we're being fancy) as a tool. So if "to swim" is a tool for fitness and recreation, maybe that helps explain why you'd say:
"I used to swim every morning before work."
But that's just a way to think about it, not how it's actually used.
Two more points, since I'm sure this is already more detailed than you wanted:
- It is always "used to," and never "use to." People get mixed up, because in spoken English, the "-d" at the end of "used" blends with the "t-" at the beginning of "to," and you don't hear the separation.
- We also use "used to" with the verb "to be" to mean "accustomed to." So: "I am used to shorter answers to simple grammar questions."
(Also, forgive me, but I hope this is helpful: unless you make costumes for actors, you're probably a customer, not a costumer, though since this board is a free service, you're probably neither.)