what is the difference between "en" and "dans"? is "dans" used as a prepositional phrase like "dans mon sac a dos"?

The word "en" is either an indefinite pronoun, an adverb or a preposition. As a preposition it means "in, into" such as "to go to France." = Aller en France. En mer = at sea. "en congé" = on leave. "en chemin de fer" = by rail. "en bois" = (made) of wood. The meaning can be very varied, dpending upon the context, or exactly how the word is used. (in, into, at, on, by, of, as)

The word "dans" is a preposition only, meaning "in; into; in (at the end of). Some expressions are "dans deux jours" = in two days...boire dans un verre = to drink out of a glass...dans la suite = later

There are quite a few idioms using "en" and here are some:
en automobile, avion, bateau, chemin de fer, voiture = by (inside the means of transportation) automobile, plane, boat, train, car

en arrière = backward(s), behind

en bas = downstairs
en haut = upstairs

en effet = (yes) indeed, as a matter of fact

en face de = opposite

en famille = as a family, within the privacy of the family

en même temps = at the same time

en plein air = in the open air, outdoors

en = late (not on time)

en tout cas = in any case, at any rate

en ville = downtown, in (to, into) town

Yes, "in/within" my backpack was a good example of using "dans."

Just take the expressions as you meet them.

Sra (aka Mme)

this is confusing. so sometimes when a phrase using "en" is translated into english, the "en" doesn't mean anything? do you know what year of french this is taught in?

merci beaucoup!! vous etes super!

Yes, you are correct. "Dans" and "en" are both prepositions in French, but they are used in different contexts.

1. "Dans": It is used to indicate location or position within a specific space or area. For example, "dans la maison" means "in the house" and "dans mon sac à dos" means "in my backpack." It shows that something or someone is physically inside a particular place.

2. "En": It has multiple uses, including indicating location, time, manner, and material. Here, we'll focus on its usage as a preposition of location. "En" is used to express being in or on something more general or abstract, often when there is no physical boundary or containment involved. For instance, "en ville" means "in the city" and "en France" means "in France." It suggests being within a larger, less confined area.

In summary, "dans" is typically used when there is a specific, enclosed space involved, while "en" is used for more general or abstract locations. Remember that prepositions in any language can sometimes have exceptions or variations, but these guidelines capture the general usage of "dans" and "en."