Hi. I'm a big fan of this site, for many reasons, so I am pointing this out in a spirit of collaboration, not criticism: I think this page should refer to "present continuous" and "present participles", not gerunds.
The gerund is a form, derived from a verb, which ends in --ing, but it is the noun from the verb. This page is all about an alternative verb form.
For example: "Smoking is bad for you."
"Smoking" is a gerund, as it has become a noun.
"That man is smoking" is the present continuous form of the verb. "Smoking" in this sentence is the present participle, i.e. not a gerund.
I am prepared to accept that this might be a US/UK English thing; I'd be very interested to hear if this were the case.
Best wishes
Andrew Wenger