1. -- ( ), Dashes, Parentheses and Commas are tools used in writing to set off or provide further information about a topic in your sentence. However, while they all serve a similar purpose they have specific circumstances which each is best utilized under.

2.  Dashes indicate the most emphasis out of all three punctuation marks. They are used to set off a short phrase or subordinate clause at the end of a sentence to provide further or significant information about the subject of your sentence.  Jean Robear was a very good dog--he always listened to his master.

3.  Parentheses are used for clarifying information, afterthoughts and examples. Parentheses may contain a few words, fragments or full sentences. They also indicate an amount of emphasis slightly less than the dash.  Leo Tolstoy (widely know as Russia’s greatest novelist) is one of my favorite authors.

4.  Commas provide the least amount emphasis among the three forms of punctuation. They are used to enclose information that adds to, explains or deviates from the sentence.  Rupert, the repair man, was quite rude to Mrs. Ringwald while he was fixing her leaky faucet.