The meaning "is" or "are" may be expressed by the copula desu, and by the verbs arimasu and imasu. The copula desu is used when one thing is, or equals, another; arimasu refers to the existence of inanimate objects (including plants, which don't move about); and imasu refers to the existence of animate objects.

Here is a table summarizing these words: 

Desu and Da 

The copula "desu", and its plain form "da" express the equivalent of the English words "is" and "are", but is always placed in the end of a clause. The polite version, "desu", can be used in most situations, but often feel too formal when talking to family and close friends. Then the plain form "da" is more commonly used.

Please note that usage plain forms in Japanese can be considered rude if you are not close.  

ここは横浜駅です。
Koko wa Yokahama eki desu.
This is Yokahama station. (polite)

ここは横浜駅だ。
Koko wa Yokahama eki da.
This is Yokahama station. (plain / casual form)

Arimasu and Imasu 

喫茶店は銀行と郵便局の間にあります。
Kissaten wa ginkou to Yuubinkyoku no aida ni arimasu.
The coffee shop is between the bank and the post office.

わたなべさんはどこにいますか。
Watanabe san wa doko ni imasu ka.
Where's Mr. Watanabe?

銀行はどこにありますか。
Ginkou wa doko ni arimasu ka.
Where's the bank?

Negative Use - Is Not

The negative of desu is dewa arimasen or ja arimasen or dewa nai desu or ja nai desu. When describing the location of something, ni arimasu can often be replaced by desu. The verb arimasu can often be translated as "there is", "are" or "have".

アメリカ人ではありません。イギリス人です。
Amerikajin dewa arimasen. Igirisujin desu.
I'm not American. I'm English.

誰もいません。
Daremo imasen.
There is noone (here). 

三円もありません。
(watashi wa) San en mo arimasen.
(I don't) even have 3 yen.  

Polite Forms

In situations demanding a high degree of courtesy, e.g., a sales clerk in a department store talking to a customer, the speaker is likely to use the formal and humble gozaimasu instead of arimasu and irasshaimasu instead of iru.

このホテルには、ファックスがありますか。はい、ございます。
Kono hoteru ni wa, fakkusu ga arimasu ka. Hai, gozaimasu.
Do you have a fax in this hotel? Yes, we do.

すみません、このセーターはいくらですか。それは９０００円でございます。
Sumimasen, kono seetaa wa ikura desu ka. Sore wa kyuu-sen en de gozaimasu.
Excuse me, how much is this sweater? It's 9,000 yen.

もしもし、田中さんはいらっしゃいますか。
Moshi, moshi. Tanaka san wa irasshaimasu ka.
Hello. Is Mr. Tanaka there?