Conjugation:
To conjugate means to change a verb (an action) into the different people and tenses. For example:
I eat, you eat, he eats, we eat, you all eat, they eat.

You need endings in Spanish to conjugate. Every verb in Spanish in its original form ends in Ar, Er, or Ir. For example: hablar (to talk), comer (to eat), vivir (to live).
All the verbs that end in Ar (like hablar, nadar, pasar, etc.) have the endings: o, as, a, amos, ais, an.
Every ending corresponds to a person or persons. Before you can add the ending you must take off the "ar." For example: "hablar" goes to "habl" and then to "hablo"

o=yo (I) Hablo (I speak)
as=tú (you) hablas (you speak)
a=él/ella/usted (he, she, it, you formal) habla (he speaks)
amos=nosotros (we) hablamos (we speak)
áis=vosotros (you all) habláis (you all speak)
an=ellos/ustedes (they, you all) hablan (they speak)

Verbs that end in Er (like comer/to eat) have these endings:
o=yo Como (I eat)
es=tú Comes (you eat)
e=él/ella/usted Come (he eats)
emos=nosotros Comemos (we eat)
éis=vosotros Coméis (you all eat)
en=ellos/ustedes Comen (they eat)

Verbs that end in Ir (like escribir/to write) have these endings:
o=yo Escribo (I write)
es=tú Escribes (you write)
e=él/ella/usted Escribe (he writes)
imos=nosotros
ís=vosotros
en=ellos/ustedes