Linkback, the suite of protocols that allows websites to manually and automatically link to one another

Pingback, a similar protocol less prone to spam

Webmention, an alternate implementation of the pingback protocol that avoids the complexities of xmlrpc.

Refback, another similar protocol

Referer, identifies the address of the webpage of the resource which links to it

Sping, short for "spam ping"

image trackback

define trackback

wikipedia trackback

weblio trackback

kotobank trackback

jisho trackback