An article is a word that modifies a noun in a particular way, by stating whether the noun is specific, unspecific, or partial. There are three types of French articles, and they all agree in gender and number with the nouns they modify.
Avoir is one of the two most important French verbs and has irregular conjugations in just about every tense and mood. Avoir literally means "to have" but also serves an an auxiliary verb and is found in many idiomatic expressions.
Contractions occur when two words are combined into one, sometimes with a distinctly different spelling. In English, contractions like "won't" are optional and indicate informality. In French, however, contractions are required, regardless of the register you're speaking or writing in.
The preposition dans usually means "in," but as always there are exceptions. Dans can't be followed directly by a noun - it's always followed by some kind of determiner, such as an article or possessive adjective.