What does “KHTML, like Gecko” mean in a user-agent string?

Konqueror began to pretend to be “like Gecko” to get the good pages,
and called itself Mozilla/5.0 (compatible; Konqueror/3.2; FreeBSD) (KHTML, like Gecko).

For more information, read:

• Andersen, Aaron (September 3, 2008) –
  History of the browser user-agent string – WebAIM