I presume that you are asking about 'did' and 'didn't' as auxiliary verb in the past simple tense. We mainly use these auxiliary verbs for negatives and questions. For example: Você falou = You spoke (past simple form) Você falou? = Did you speak? (Did + base form) Você não falou = You didn't speak (Didn't + base form) We also use them in tag questions: Você foi à escola, não foi? = You went to school, didn't you? And we also use 'did' to add emphasis: A: Why didn’t you come last night? (Por que você não veio ontem à noite?) B: I did come! (Eu vim sim!) I hope that answers your question.

*How do you use did and didn't? This is a very broad question. Did is the action of doing, and didn't (did not) means that the action was not done (completed)

para el Pasado simple, did es afirmativo,Did se usa para interrogativo(preguntas) y repuestas afimartivas,,,ej: Did you do the homework?..yes,I did,I already did it! Generalmente lo usas cuando trabajas en pasado, si aplicas este verbo auxiliar el siguiente verbo debe de ser en presente. Ejemplo: Did you eat bread? aquí te das cuenta que eat está en presente pero si fuera una afirmación sería "You ate bread" ate es el pasado de eat, y también date cuenta que si negas una oración en pasado quedaría "You did not eat bread" el verbo regresa de nuevo a presente. Didn´t----es lo opuesto/contrario de Did, aquí se hace aclaraciones negativas(preguntas y respuestas) ej:didn´t you buy a new car? ,,no,I didn´t..I didn´t buy it because I was needing money. nota:cuando vayas hacer alguna pregunta con alguno de ellos siempre toma en cuenta que el verbo que le sigue este en presente..ej:did you (brush) your teeth? yes,I did..I brushed my teeth before coming here... didn´t you (come) yesterday? no,I didn´t.I couldn´t come because I was tired... no pongas...did you xatex yesterday? didn´t you xwentx to the cinema yesterday night? JUAN NEFTALI"

Did and Didn't in English Language. Did is an auxiliary verb, it is past simple of Do. They are used with another verb to form questions and negative sentences. Where did she go? Did they find water on Mars? Yes they did. No they didn't. How many pies did he eat?