@Fire69:

In most cases the "de" structure equates to our English sentence pattern,

The...that, the...in..., the...who, the...which, the...when

So the sentence, "Wǒ jiā de kètīng hěn dà", translates to, "the living room in my house is very big."

Putting it into the Chinese sentence structure, "My house's living room (is) very big."

"的" also has a possessive usage, EG: wǒ de lǎo pó, (my wife)wǒ de fáng zi (my house), wǒ de shū (my book), wǒ de chē (my car)