In grammar, tense is a category that expresses time reference with reference to the moment of speaking. Languages overall tend to express this by using different forms of verbs.
The gerund or present participle, (el gerundio) is the same as the '-ing' ending in English.
This tense is one of the simpler ones, since there are only a few possible endings with some irregular verbs.
Regular '-ir' / '-er' verbs form the gerund form by removing the '-ir' / '-er' ending and adding '-iendo.'
stem
aprender- aprend- aprendiendo (learning)
vivir- viviendo (living)
escribir- escribiendo (writing)
Regular '-ar' verbs form the gerund by removing the '-ar' and adding '-ando.'
trabajar- trabajando (working)
cantar- cantando (singing)
mirar- mirando (watching)
Irregular '-ir' / '-er' verbs with stems ending in a vowel form the gerund by removing the ending and adding '-yendo.'
caer- cayendo (falling)
construir- construyendo (constructing)
creer- creyendo (believeing)
destruir- destruyendo (destroying)
huir- huyendo (fleeing)
ir- yendo (going)
leer- leyendo (reading)
oír- oyendo (hearing)
traer- trayendo (bringing)
Stem-changing '-ir' verbs change their stem vowel from e to i or from o to u.
decir- diciendo (saying)
dormir- durmiendo (sleeping)
morir- muriendo (dying)
pedir- pidiendo (asking for)
sentir- sintiendo (feeling)
venir- viniendo (coming)
conseguir- consiguiendo (obtaining)
corregir- corrigiendo (correcting)
mentir- mintiendo (lying)
repetir- repitiendo (repeating)
servir- sirviendo (serving)
vestir- vistiendo (dressing)
The gerund can be used in the same way as 'by (present participle)' in English.
Trabajando, se gana dinero. By working, one earns money.
Estudiando, aprendes mucho. By studying, you learn a lot.
The gerund can also be used to form the progressive tenses.
The present progressive
The present progressive is formed by adding the conjugated form of the verb 'estar' before the gerund.
Los muchachos están llorando. The boys are crying.
Estoy estudiando para aprobar la prueba. I am studying to pass the test.
The gerund can also be used with the verbs seguir, continuar, andar, venir and other verbs of motion.
Siguen escribiendo. They continued writing.
Continuaban hablando. They continued speaking.
Andaban cantando. They were walking along singing.