Though sideburns have been around for as long as facial grooming, it wasn't until Civil War Gen. Ambrose Burnside sported an exaggerated example that they got their English name. Depending on the era and the culture, different sideburns styles have come in and out of favor. Different sideburns styles include ones just the length of the ears, long skinny spikes, and the iconic mutton chop, among others. One thing remains unchanged, though: Once those sideburns connect from ear to ear across the chin, they're no longer sideburns and have become part of a beard.
Perhaps the most common consideration regarding sideburns styles is how far down the ear they will be allowed to grow before they get trimmed. Some men choose short sideburns by shaving down from the very the top of the ear, where the hairline begins. Some leave 0.5 inch or 1 inch (1.27 or 2.54 cm) of hair extending down from the top of the ear, or even all the way to the ear lobe. These sideburns are then kept trimmed or allowed to get bushy. The rest of the face is then kept clean-shaven.
Often, a desire emerges to cultivate even longer, grander sideburns. This is especially the case for those with longer faces and chins or those looking to complement a full mane of hair. Some men shave their sideburns into skinny spikes that extend well below the ear lobes; others let their sideburns grow far down their cheeks but keep them trimmed on the sides for a uniformly squared-off appearance. For a man with a shaved head, swooping sideburns provide a point of interest on an otherwise blank canvas.
One of the more iconic sideburns styles also extends well down the face, but also flares out in the natural pattern of the male beard. These are called mutton chops. They can be crafted in a shorter style with moderate flaring or they can be long, widely flared and as thick as genetics will allow.
The sideburns style made popular by General Burnside in the mid-19th century isn't anything like the most common styles of the 21st century. Burnside's combined the mutton chop with a bushy mustache, while keeping the chin shaven, perhaps to avoid trapped food. This is now called the friendly mutton chop, and the thicker the tufts of facial hair that radiate from the jowls, the better.