What happens when you conjugate a verb in the past (preterite) tense? give me an example with a spanish sentence and explain how it differs from present tense conjugation.

Okay so, feel free to change my words if it's for an assignment, if not, then I will explain.

Preterite tense is basically past tense in english. Saying, " I went to the movies with my friends" in spanish using preterite tense would be "Yo fui al cine con mis amigos."

Went, is a form of going, so go is ir in spanish, and you wouldnt say " yo ir al cine" because it wouldn't be used in past tense also it's just plain wrong. It would be "me voy al cine" if it was in present tense.

Using past preterite tense would be "Fuiste al cine?" Asking if you HAD went to the move theaters. It is different from present tense because one, the word has a different ending. "Ellos fueron al cine con sus padres." "They went to the movies with their parents. "

I hope these examples helped you, also, for future help I recomend using Spanishdict.com.  It gives a lot of help when it comes to spanish conjugation.