A cardigan is a type of sweater (or jumper) that ties, buttons or zips down the front; by contrast, a pullover does not open in front but must be "pulled over" the head to be worn.
The cardigan was named after James Brudenell, 7th Earl of Cardigan, a British military commander, following his service in the Crimean War.
Plain cardigans are often worn over shirts and inside suit jackets as a kind of less formal waistcoat or vest that restrains the necktie when the jacket has been removed.
This is one of my favorites items and by the time I had all this photographs, a big note and the perfect picture, as usual, from the The Sartorialist:
"As holiday season approaches, gift giving is on most peoples mind. So ladies, if you want to buy one item that will dramatically affect the look of your man then buy him a cardigan. As you can see from this shot, this gentleman would look great with just the shirt and jacket. However, he looks so much more refined (while maintaining a casual feel) by adding the cardigan. The cardigan can also be very slimming. It eliminates that hard visual line where the shirt meets the pants and reigns in the visual paunch of a shirt that blouses out too much at the waist. I was thinking about doing a set of "gift giving" posts. Little gifts that have a huge impact on a man's look. I guess I'm getting ahead of myself because a good cardigan would be at the top of my list."