Sway bar end links are the attachment points between a sway bar and suspension members. Also known as a stabilizer bar or anti-roll bar, the sway bar connects suspension components on either side of the car to minimize body leaning in turns.
Different types of sway bar link bushings are available such as polyurethane instead of rubber. They will give a slightly different feel handling wise as they are stiffer, so this might be a consideration if you are wanting an upgrade over OEM.