Verbs in the present tenses reflect actions that happen or are happening at the moment of speaking:
Tengo dos coches.
I have two cars.
(Tengo reflects a present action)
Verbs in the past tenses reflect actions that happened, were happening, had happened in the past, i.e. prior to the present time:
Ayer vi a Laura.
I saw Laura yesterday.
(Vi reflects a past action)
Verbs in the future tenses reflect actions that are still to happen, at a future moment:
Mañana iré a la playa.
I will go to the beach tomorrow.
(Iré reflects a future action)
Note: Tenses communicate more nuanced details of time than merely 'past', 'present' or 'future'. They can convey time relative to other events, whether actions finish(ed) or are/were ongoing, even things that are 'out of time': imagined events, events that could happen, or that we hope will or won't happen.
See: Tense / Mood