A famous example: A panda walks into a cafe. He orders a sandwich, eats it, then draws a gun and fires two shots in the air. “Why?” asks the confused waiter, as the panda makes towards the exit. The panda produces a badly punctuated wildlife manual and tosses it over his shoulder. “I’m a panda,” he says at the door. “Look it up.” The waiter turns to the relevant entry, and sure enough, finds an explanation. “Panda. Large black-and-white bear-like mammal, native to China. Eats, shoots and leaves.” (from a book on punctuation by Lynne Truss)

"She is a Japanese art student." So... is she an art student who is Japanese, or is she studying Japanese art? The way the sentence is written above, it means she is a Japanese woman studying art. If you wanted to say she was a woman of any nationality studying Japanese art, you would need to add a hyphen between "Japanese" and "art." Here's another example: "My brother, who lives in Florida, is 50 years old." By adding two commas, I've created a clause that tells the reader that I have one brother who is 50 and lives in Florida. But if I remove the commas, it tells that reader that my brother IN FLORIDA is 50, and implies that there is another brother who lives somewhere else and is a different age.

It's definitely important. Don't let anyone tell you otherwise. Simple example: compare "Let's eat, Grandma!" and "Let's eat Grandma!"

Basic English Punctuation Rules www.esl.about.com

Punctuation is important in the english language, but many people use it incorrectly. The most common mistakes are made using the apostrophe ' It is such a problem that many academics tell people not to use the apostrophe if they don't understand its use. Examples can be seen using this link: http://www.apostrophe.org.uk/