Can someone tell me the difference between preterito indefinido and preterito perfecto?

Pretérito Perfecto

the pretérito perfecto, or perfect tense is used for actions that take place in a time frame that has not yet ended, or for past actions that continue to influence the present.

*action is completed, but in a time period that still counts as the present in Spanish (este semana, hoy)

Example:

La primera clase ha sido esta mañana y me ha encantado.

*completed action that has an influence on the present or the future

Example:

He decidido comprar un bono anual de entrenamiento.

Preterito Indefinido

The indefinido, or preterite tense, is used for completed past actions

action completed at a point in time that counts as the past in Spanish (see signal words, below)

Example:

La semana pasada me apunté a unas clases de tenis.

Lo primero que hice fue comprarme una raqueta en la tienda de deportes de la esquina.

Hope this helped!!!

~BBGLUVER

ok i dont know what b says but d is the only one that sounds some what like an aperitivo