There are several different words which all translate to the English word "the". There are rules when to use each word, but if your goal is just to know basic Yiddish, it's not so important to actually know these rules.
These words are also used to mean "this". When it means this, more emphasis is given to the word.
Another common word, which has already been used in some of the examples, is איז. It is usually pronounced exactly like the English word is, but sometimes the ז at the end is left unpronounced. It means the exact same thing as the English word is.
Here are a few more common words:
The word ניט is very often used together with קײן, which is somewhat hard to translate. It usually replaces the word אַ or אַן before a noun.