There are several little statement in this statement. Let' s discuss about it step by step.

1) The imperfect is much mor frequently used in Italian than in English.
That' s quite easy to say, but difficult to proove statistically and from a pure logical point of view it doesn' t seem very plausible. We presume that he want to say that the Italian imperfetto is used more often than the English simple past. Is that plausible from a logic point of view? The functions of the English simple past is realised in Italian by TWO tenses, the imperfetto and the passato remoto (or with the passato prossimo in modern Italian). Therefore it is much more plausible that the imperfetto is less frequent than the simple past in English. Perhaps things became more understandable with an example.

a) To describe a singular action in the past, we use the simple past in English, but the passato remoto / passato prossimo in Italian.

I sold my car.
Ho venduto la mia macchina. / Vendei la mia macchina.

b) To describe an action which happens regularly in the past.

x) I used to read the newspaper every morning.
xx) Leggevo il giornale ogni mattina.

As you can see in these examples, the English simple past has two different functions, but these functions are distributed in Italian on two different tenses.

2) It expresses the English "used to" and is used to describe actions or conditions that lasted an indefinite time in the past.

That' s right. The Italian impferfetto describes actions which happens regularly in the past, in this case we use the perifrasis 'used to' in English and actions which are 'indefinit', in other words, actions where the beginning and the end is not known or irrelevant.

a) Action which happens regularly in the past
I used to bake my bread myself.
Di solito facevo il pane io stesso.
b) Indefinite action, where the beginning and the end is unknown or irrrelevant
The book was on the table.
Il libro era sulla tavola.

The error in the statement above is that the English simple past has a third functions, actions which happens only once in the past (He left the room) are described with the simple past as well, therefore it is not possible to equate the Italian imperfetto with the English simple past.

It's also used to express an habitual action in the past and to describe time, age, and weather in the past.

This statement is somehow weired. The 'habitual action' has already been mentioned, these are actions which we describe with the periphrases 'used to' in English. A periphrasis is a verbal construction which includes the meaning of an adverb or an adverbial adjunct.

I used to read the newspapers every morning.
Normally I read the newspapes every morning.

There are no similiar periphrases in Italian. In Italian this kind of construction has to be translated with an adverb. (There is a similar construction in Spanish though: Solía leer los periódicos por la mañana.) The problem with this statement is that it suggests that the simple past can be translatet always with the Italian imperfetto. That' s not the case, because singular actions in the past are described with the simple past as well, but never with the imperfetto. Singular actions are described in Italian with the passato remoto (in the classical literature) or with the passato prossimo, in modern Italian.