What are German articles?
The German language uses grammatical genders. This means that the language has different categories that a noun can fall into. German isn't the only language to use gender. Spanish and French are among the many other that use them too.
In German there are 3 genders: masculine, feminine, and neuter. Each gender has its own article. In English we use the article "the" to refer to any noun. It never changes. In German the word "the" will change based on the gender of the noun you're talking about.
German articles vs English articles
Why are German articles important?
When you use a masculine, feminine, or neuter word in German, you have to use the article that agrees with its gender (you can't say das Tisch). If you do you'll be incorrect and will immediately sound strange to native speakers.
What makes German articles so hard?
What makes the German articles so hard is that it's not always easy to remember the gender of German words. Grammatical gender has nothing to do with the nature of the noun and there are often exceptions to the trends of gender in the language.
For example the word for girl: Mädchen is neuter even though you'd think it should be feminine.
Sometimes you can even have two words for the same object and those two words will have different genders:
Tips for learning German articles
Learn nouns with their articles
When you practice or review German nouns, always do so with the correct article. This will get you in the habit of remembering which gender a word has.
When in doubt don't guess neuter
Only around 20% of German nouns are neuter. If you're unsure of the gender of a word try guessing feminine or masculine. Chances are more likely you'll be correct that way.
Practice rather than memorize
Rote memorization works for some people learning German articles but for the majority of learners it's neither effective nor fun. Don't spend too much time mindlessly drilling German nouns and articles. The best way to practice is to listen to them used correctly and then try to use them yourself.
Listening to native audio is a great way to practice. If you're a beginner try listening to a German radio station, video, or podcast and pick out all the nouns you know, making note of which article they're used with.
Make sure when you practice German (whether speaking or writing), you have some way to get feedback from native speakers.
Odds are that you'll mess up the articles a lot in the beginning. You need someone to point out your mistakes so you can correct them. Before long the articles will feel more comfortable.
Learn the rules:
While there are some unexpected exceptions to German article rules, here are some rules you can use to cut down on the confusion:
Words ending in -heit, -keit, -ung, or -schaft are always feminine
If you see a noun with any of these endings use the article die.
Words ending in -ling or -ismus are always masculine
If you see -ling or -ismus in the noun you can be sure that it's masculine.
Diminutive nouns ending in -chen or -lein are always neuter
As long as the noun is diminutive and ends in -chen or -lein you can be sure that it is a neuter noun.
German articles aren't a walk in the park, but they are far from impossible. With some time and effort you will see yourself become more familiar with them, even to the point where you'll no longer have to think about which article to use with which word!