C. A Clause is a basic unit of English next below the sentence in rank and in traditional grammar said to consist of a subject and predicate. (e.g. (A supermoon occurs) (when the Moon is in its closest part of orbit to Earth,) (making it appear larger in the sky.) (This phenomenon of the lunar eclipse and 'supermoon' together was last observed in 1982) (and will not come again until 2033.))
a. The Clause is made up of Phrases. (e.g. (A supermoon) (occurs) (when) (the Moon) (is) (in its closest part of orbit to Earth,) (making it) (appear) (larger in the sky.) (This phenomenon of the lunar eclipse and 'supermoon' together) (was) (last observed in 1982) (and) (will not come) (again) (until 2033.))
b. Clauses can be joined two or more to make Sentences. (e.g. A supermoon occurs when the Moon is in its closest part of orbit to Earth, making it appear larger in the sky.) (This phenomenon of the lunar eclipse and 'supermoon' together was last observed in 1982 and will not come again until 2033.)

C1. All Clauses in English have at least two parts: a Noun Phrase and a Verb Phrase. (e.g. The super moon appeared.: The super moon (Noun Phrase) + appeared (Verb Phrase))
a. English Clause always have a Subject, the first Noun Phrase is the Subject of the Sentence. (e.g. The super moon appeared: The super moon (Subject) appeared), except for the imperative clauses. (e.g. Be careful! Please come on over here)
b. If we have no other subject we use 'there' or 'it' as subject (= dummy subject). (e.g. There will be an eclipse of the moon tonight. It was a beautiful phenomena.)

C2. Clause types: Declarative, Interrogative, Imperative, and Exclamative clause
a. Declarative clauses (statement) are used to convey information or to make statements. The usual word order is subject (s) + verb (v) + ~. (e.g. Ann plays the piano.)
b. Interrogative clauses (question) are used in asking questions. The usual word order is (Wh-word) + auxiliary/modal verb + subject + verb + ~. (e.g. Did you receive Jon's letter?)
c. Imperative clauses (order or instruction) are used in issuing orders or directives. The usual word order is verb + ~. (e.g. Give me your home address.)
d. Exclamative clauses (exclamation) are used to make exclamations. (e.g. How wonderful you look!)

more about the English Structure ...