Grammar

SIMPLE SENTENCE
A simple sentence, also called an independent clause, contains a subject and a verb, and it expresses a complete thought. In the following simple sentences, subjects are in yellow,and verbs are in green.  
Some students like to study in the mornings.
Juan and Arturo play football every afternoon.
Alicia goes to the library and studies every day.
The three examples above areall simple sentences.  Note that sentence B contains a compound subject, and sentence C contains a compound verb.  Simple sentences, therefore, contain a subject and verb and express a completethought, but they can also contain a compound subjects or verbs. 
COMPOUND SENTENCE
A compound sentence contains two independent clauses joined by a coordinator. The coordinators are as follows: for,and, nor, but, or, yet, so. (Helpful hint: The first letter of each of the coordinators spells FANBOYS.) Except for very short sentences, coordinators are always preceded by a comma. In the followingcompound sentences, subjects are in yellow, verbs are in green, and the coordinators and the commas that precede them are in red. 
I tried to speak Spanish, and my friend tried to speak English.Alejandro played football, so Maria went shopping.
Alejandro played football, for Maria went shopping.

The above three sentences are compound sentences.  Each sentence contains two independent clauses,and they are joined by a coordinator with a comma preceding it.  Note how the conscious use of coordinators can change the relationship between the clauses.  Sentences B and C, for example, areidentical except for the coordinators.  In sentence B, which action occurred first?  Obviously, "Alejandro played football" first, and as a consequence, "Maria went shopping.  In sentence C, "Maria wentshopping" first.  In sentence C, "Alejandro played football" because, possibly, he didn't have anything else to do, for or because "Maria went shopping."  How can the use of other coordinators change...