Mark is a logical person who has a career in a credit company; has his sights set on the girl of his dreams, Sophie; and is completely uncomfortable with himself.
Jeremy, on the other hand, is more than comfortable with himself, to the point of narcissism; he falls 'in love' so often, one questions his understanding of the word or his capacity of genuine emotions; and finally, his job is an aspiring musician.
Over the series you see their antics as they try to cope with the world around them as well as each other.