What is an Article?
Certain words in German have a grammatical gender. Those genders are masculine (m), feminine (f) and neuter (n). The only words that have a gender are called nouns. Those are words that in English can be used with the. So house is a noun because you can say the house. And that's why the German equivalent for house - Haus is also a noun and it's of neuter gender - das Haus.
The Three Magic Words
You need to nail the whole article thing in German if you want to sound proper and smart. Luckily, you can learn to easily recognize which base article a German noun needs in ~25% of the cases.
You don't even have to understand the word in question. All you have got to do is to learn three magic words. They are difficult words because they don't make any sense but with a bit of practice you'll memorize them for good:
derIg-ling-or-ismus+er
dasTum-chen-ma-ment-um-lein+nis
dieHeit-ung-keit-ei-schaft-ion-ie-tät-ik+ur+e
The words above consist of the most popular word-endings for each gender that give away the article of a specific word.
Examples
- Käfig ends in -ig - needs the article der
- Mädchen ends in -chen - needs the article das
- Freiheit ends in -heit - needs the article die
Notice: The + sign before a syllable means that the following syllable is not 100% consistent. For example "Butter" ends in +er but is feminine. They are still ~80% reliable which qualifies them to be part of the three magic words.