En is a French word that can replace phrases starting with de. Examples:
- Comment pouvons-nous en savoir plus sur cet individu ? (How are we to know anything further about this individual?) The en stands in for de choses, e.g. Comment pouvons-nous savoir plus de choses sur cet individu ?
- Je m'en vais. (I'm leaving.) The en stands in for d'ici or de [place].
En can also be used as a preposition, e.g. with a present participle, as in en passant (in passing).
A guideline about when to use en or dans is that when you want to say "in the", "in a", "in my", "in your", "in a few", basically, when the "in" is followed by an article, you should use dans. When the "in" is not followed by any article, it will most likely be en.