Meryl explained the it pretty well, but just to give a bit further,
moji means all of the different kinds of characters, and
kanji are exactly the same as the Chinese ones, because they were taken directly from it.
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Desu is a linking copula, similar to the English, "to be". However unlike, "to be" it does not change it's form according to it's subject.
Desu is also always placed at the end of the sentence.
The negative of
desu is
ja arimasen (not to be) or
de wa arimasen (meaning the same thing, but more formal, and less common).
Ex.
Watashi wa gakusei desu.
I am a student.
Kochira wa Suzuki san desu.
This is Ms. Suzuki.
Watashi wa gakusei ja arimasen.
I am not a student.
Watas.h.i.tachi wa sensei ja arimasen.
We are not teachers.
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Also, a few more useful phrases for conversation.
Anata wa nihonjin ja arimasen.
I'm not Japanese.
(*In most cases you can leave out personal nouns such as
watashi/anata/kare/kanojo wa if the context of the sentence is still clear without them.)
Watashi wa eigoga hanashimasu/wakarimasu.
I speak/understand English.
Baka!
Idiot!
(*You can however have this interperated many different ways determined by context, intonation, etc.
)
Ii desu ne.
That is a good idea/sounds nice.
Ikage desu ka?
How're you?
Sumimasen.
Excuse me/Thank you/Sorry.
Domo arigatou gozaimasu.
Thank you very much.
(*Can exclude
domo or
gozaimasu depending on how much gratitude is being given).
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Is this too much/too little?
Give me comments on the lessons I'm posting.
:p