"Molto" can function as both an adjective and an adverb.
When used as an adjective, the ending of the word should change to match the noun it's modifying ("molta gente," "molti problemi," etc.). When used as an adverb, you can only use "molto"; the ending doesn't change ("parliamo molto," "molto buono," etc.).
It's hard to tell exactly what you're referring to, but my guess is that the lesson focused on odd noun endings that come up frequently in Italian. Like words that end in "-ione" and "-tà," words that end in "-ma" do not follow the default rules for masculine/feminine endings and pluralization.