Conjunctions, like prepositions, relate words and word groups.
1. Coordinating conjunctions:They link words or word groups of the same type:
and    for    or    yet
but    nor    so
Maher and Salwa have little in common. ( two nouns linked)
Samer skydives, but Philip is afraid of heights. ( two independent clauses linked)
Philip must choose whether to read or to write. ( two infinitives linked)
2. Correlative conjunctions:They are word pairs that link words or word groups of the same type:
both . . . and        neither . . . nor
either . . . or        not . . . but        not only . . . but also
Both Maher and Salwa play chess. ( two nouns linked )
They neither smile nor frown during a game.  
3. Subordinating conjunctions:They link clauses so that one clause is incorporated as a modifying part of another clause. Some subordinating conjunctions are although, because, if, unless, while.
Ahmad came to school although he was ill.

The subordinating conjunction although makes the clause he was ill subordinate to the clause Ahmad came to school. The subordinate clause tells something about the conditions under which Ahmad came to school. It is actually an adverbial modifier that can be moved within the sentence:
Although Ahmad was ill, he came to school.
4. Conjunctive adverbs: Independent clauses may be linked not only with coordinating conjunctions but also with conjunctive adverbs. In  linking two independent clauses, a conjunctive adverb modifies the clause following it.
The flood left ten inches of mud in the hotel. Nevertheless, the Optimist Club held its regularly scheduled meeting there.
Common conjunctive adverbs are listed below:  
accordingly        furthermore        meanwhile        similarly
also                   however            moreover          still
besides              nevertheless      now                  therefore
These words can also serve as simple adverbs.
She was finally gone.
However ugly Salem was, he will remain in our hearts.  
Reference:
Kirkland, James . W  & Dilworth , Collett. B  Concise English Handbook Houghton Mifflin Company 1983

 
أ. مسلم قمباز,  
 A very simple and clear explanation of conjunctions  
God bless you Mr. Msallam