Hello Nacera. ''used to'' - done or experienced in the past, but no longer done or experienced. For example: I used to smoke, but now I don't. I used to drink coffee, but now I don't. I prefer tea. (this is something that we used to do but now we don't do that anymore) ''use to'' is used in negative and interrogative sentences. I didn't use to smoke, but now I do. What about you? Did you use to smoke? There is another expression, as well ''be /get used to something/someone. It means to become familiar with something or someone. For example: I can't get used to getting up early. (ing verb) We are used to tourists here - we get thousands every year. I hope this helps :)

thank you so much !