In Spanish the gerund (the -ing verb form in English) is formed by taking the stem of the verb (e.g hablar → habl-) and adding one of these endings:
-ando (for -ar verbs)
-iendo (for -er/-ir verbs)
Hablar → habl- = hablando
Comer → com- = comiendo
Vivir → viv- = viviendo
Here are some more examples:
This is the rule that applies to regular gerunds.
See also Forming irregular gerunds (-ing form) .