Commas are generally used to indicate a natural breathing space. More subtle than the full stop, which brings a sentence to a juddering halt, the comma is a subtle pause and, when properly used, greatly enhances readability and understanding. Compare these two sentences:
Melanie Silver has I believe nearly 20 years’ professional copywriting experience
Melanie Silver has, I believe, nearly 20 years’ professional copywriting experience
Most people would put commas before and after the words “I believe” because it qualifies the key statement, distinguishing personal opinion from indisputable fact.
The biggest problem with commas is that we simply use too many of them so that, far from clarifying the meaning, they merely confuse. Recognising where commas are needed is an acquired skill but as a rule of thumb where dropping a comma doesn’t hinder understanding and instead helps the sentence flow, leave it out!
