Learn Italian: Ha imparato tutto il capitolo leggendo e memorizzando le parole. - He learned the whole chapter by reading and memorizing the words.

In English, we say "by reading" to explain how something was done (the means or method). In Italian, the present gerund (verbs ending in -ando or -endo) does this job all by itself. You don't need a preposition like per or con; the gerund leggendo already translates to "by reading" in this context.

How do we know who is doing the reading and memorizing here?

The Italian gerund (leggendo, memorizzando) doesn't change its ending to show who is doing the action. Instead, it relies on a strict rule: it almost always shares the same subject as the main verb. Because the main verb is ha imparato (he learned), we automatically know "he" is also the person doing the reading and memorizing.

Why is it tutto il capitolo and not just tutto capitolo?

When tutto means "the whole" or "all of the," it must be followed by a definite article (il, la, i, le) right before the noun. So "the whole chapter" is phrased literally as "all the chapter" (tutto il capitolo).

How exactly are the gerund forms leggendo and memorizzando created?