Hola Slim

The "gerundio" is used in this structure, yes. So, the gerundio here: "estoy comiendo" would be the -ing part: "comiendo" ( = eating )

In Spanish, we call "gerundio" to the -ando / -iendo forms that we use, independently to which function that word has in the sentence. However, in English, you talk about gerund or present participle (both -ing forms), but it will call a gerund or a present participle depending on the function each time. 

When the -ing form is part of a progressive tense, like here in "estar + -ando/-iendo", this would be a present participle (so we don't call it gerund in this instance)

I hope this is what you wanted clarified. 

Saludos

Inma