THE PRESENT TENSE
A Spanish verb changes its ending to show who is acting: hablar (“to speak”) becomes hablo (“I speak”), hablas (“you speak”), hablamos (“we speak”). This is conjugation, and the present tense of regular verbs is where the whole system is easiest to see.
Three classes, six persons
Every infinitive ends in -ar, -er or -ir, and that ending decides which set of forms the verb takes. Each tense then has six forms, one per grammatical person: yo, tú, él/ella/usted, nosotros, vosotros, and ellos/ustedes. Because the ending already identifies the person, the pronoun itself is usually dropped: hablo alone means “I speak.”
The regular endings
Remove the infinitive ending to get the stem — habl-, com-, viv- — and attach the ending for the person. The -er and -ir classes differ only in the nosotros and vosotros forms.
hablar → habl- + …
comer → com- + …
vivir → viv- + …
When to use it
The Spanish present covers more ground than the English one. It expresses what is happening now, what happens habitually, and — very commonly — what is about to happen.
Vivimos en Madrid.
We live in Madrid. A present state; regular -ir, nosotros.
Mañana hablo con el profesor.
Tomorrow I am speaking with the teacher. A near future, expressed with the present — Spanish does this constantly.
The irregulars you meet immediately
The most frequent Spanish verbs are irregular in the present, and several are irregular only in the yo form. Four to recognise from the start:
ser — to be (essence)
tener — to have
ir — to go
hacer — to do, to make
Every verb table on this site marks irregular forms in this color, so the exceptions are visible at a glance — see tener for a typical example.