Re: gerunds (grammar snob alert!)
The lessons on gerunds are not really on gerunds at all. A gerund is not simply the present progressive form of a verb; it's when that form is used as a noun. For example, reading is fundamental, I hate public speaking. It can be the subject of a sentence or not. I suppose they don't really have gerunds in Spanish like we have in English, because they'd just use the infinitive form in cases like the above.