Present Progressive Tense

The present progressive tense is formed with the auxiliary verb estar plus a main verb in its present participle form (e.g. estoy escribiendo). The present participle is formed with the stem of the verb plus -ando (for -ar verbs) or -iendo (for -er and -ir verbs). For example:

cantar cantando
hablar hablando
comer comiendo
beber bebiendo
ocurrir ocurriendo
vivir viviendo

In the case of -ir stem changing verbs the stem vowel changes. For example:

preferir prefiriendo
pedir pidiendo
venir viniendo

Verbs with stems that end in a vowel also have an irregular form:

caer cayendo
oír oyendo
traer trayendo

The verb estar must be conjugated to match the subject pronoun. For example:

Yo estoy comiendo. I am eating.
Tú estás cantando. You are singing.
Él está hablando. He is speaking.
Ella está bebiendo. She is drinking.
Nosotros estamos hablando. We are speaking.
Ellos están estudiando. They are studying.

Present Progressive vs. Simple Present
Just like English, Spanish uses the present progressive tense to describe actions that are occurring while one is speaking (e.g. John is writing a letter). Also similar to English, the present tense is used to describe actions that one does repeatedly or habitually (e.g. John writes a letter every morning). One difference between the two languages, however, is that in Spanish the present tense can also be used to describe progressive actions. For example:

¿Qué haces? / ¿Qué estás haciendo? What are you doing?
¿Qué escuchas/ ¿Qué estás escuchando? What are you listening to?