That’s how I learned it too, but apparently that is “traditional” grammar. In “modern” grammar any verb with the -ing ending is a gerund now according to Wikipedia.
It's not an invention of Wikipedia editors. If you just read the first paragraph of the article it explains the accepted meaning has evolved over time. It further explains "The distinction between gerund and present participles is not recognised in modern reference grammars, since many uses are ambiguous."
