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