Estas means am, is, or are. It is the present tense of the verb esti, to be. When it is the first word in a sentence, it means "It is":
La nokto estas varma. The night is hot.
Estas varma nokto. It is a hot night.
Note: Do NOT say "Ĝi estas varma nokto". Ĝi (it) in Esperanto always stands for a noun. "Nokto estas varma nokto" is repetitive and would not make any sense, so we don't use "ĝi" in this setting.
Adjectives are words like fast, good, or big, which modify a noun. Remember that a noun always ends in -o in Esperanto. Adjectives, on the other hand, end in -a:
rapida = fast, granda = big, bona = good
In Esperanto, the adjective may be placed either before or after the noun with no change in meaning. "Bona viro" and "viro bona" both mean "a good man" and both are correct. In practice, most people place the adjective before the noun.
mal- is a prefix that means "the opposite of". Please note that while malbona means bad,mal- by itself does not mean bad (as it does in some other languages).
-ej is a suffix used to indicate a place:
kafo = coffee; kafejo = café (a place where you drink coffee, and other drinks.)
Adverbs (usually -ly words in English) modify verbs and adjectives. In Esperanto they almost always end in -e. Examples:
rapide = quickly, malrapide = slowly, bone = well
The noun following a preposition normally takes a simple -o ending (-oj in the plural). Other endings will be explained later. For example:
La virino estas en la kafejo.
The woman is in the café.
Ni iras al la parko.
We go to the park.
Ĉu introduces a yes/no question. Unlike in English, the subject and verb do not need to be inverted:
La kafo estas varma. Ĉu la kafo estas varma?
The coffee is hot. Is the coffee hot?
EXPRESSIONS WITH ĈU
Ĉu ne? = Isn't it?
Ĉu? = Really?