IMHO, the presentation of "avoir envie de" in this lesson seems to be rambling and less precise than the corresponding "avoir besoin de" lesson. (They were written by the same author.)
Because of the differing presentations, it took me a couple of re-reads to realize that the construction of these expressions is actually IDENTICAL:
- avoir besoin de + (article) + noun
- avoir envie de + (article) + noun
- avoir besoin de + infinitive
- avoir envie de + infinitive
Note that I've replaced the unnecessary "de/d'" by the simple "de", because at this stage of a French course, I don't think anyone would ever say (or write) "J'ai besoin de un crayon". [BTW: I'm impressed by the spell checker. It flagged "de un" ! ]
The use of "parallel text" causes most Brits to prefer US courses. Although the subjects might be of equal complexity and difficulty, the Yanks use parallel text for the overhead projectors and the course notes. That seems to make the subjects seem simpler - both to learn and to remember.
BTW: Parallel text simply means the use of identical text throughout - except for the differing key words. Look at my "besoin" and "envie" examples above. The differing key words seem to jump out of the page - as if they had been emboldened.