NOUNS AND PRONOUNS - Subjects, verbs, and objects

           S      V
(a) The sun shines
        (Noun)  (Verb)
          S      V
(b) Plants grow
      (Noun) (Verb)
An English sentence has a Subject (s) and Verb (v). The Subject is a noun. In (a): sun is a noun; it is the subject of the verb shines.
         S        V         O
(c) Plants need water
    (Noun)  (Verb)    (Noun)
       S          V          O
(d) Bob is reading a book.
      (Noun)   (Verb)       (Noun)
Sometimes a verb is followed by an Object (O). The Object of a verb is a noun. In (c): water is the object of the verb need.