Throughout the Star Wars saga, Jedi are referred to as Knights whereas their Sith counterparts are typically Lords. As with any other fantasy or science-fiction franchise, the specificity regarding character names, factions, and various other aspects of Star Wars can get complicated. This is especially true regarding whether or not to capitalize the light and dark sides of the Force, as well as determining if Kylo Ren is a Sith, but there's much more to the series than those things.
Given the countless differences between Star Wars Legends and canon, quite a bit of the saga's nuance can get lost along the way. Fans can see this take shape with regards to Sith history and how much of the Old Republic still exists in canon. But one of the most intriguing things is something people tend to look past, simply because it's become so commonplace in the franchise: Ever since George Lucas' original Star Wars movie released, there have always been Jedi Knights and Sith Lords, not Jedi Lords and Sith Knights.
Obi-Wan Kenobi told Luke Skywalker that the Jedi Knights were guardians of peace, and that's because Lucas was basing the Jedi Order on real-life religious institutions like the Knights Templar. The Jedi weren't meant to hold titles of nobility since they were devoted entirely to ensuring peace in the galaxy and protecting the Republic; attachment wasn't permitted, for example. Furthermore, the Jedi ruled by committee so that no one person could control them all. The Sith were the opposite; in fact, they fully believed in power, referring to themselves as Dark Lords.
For thousands of years, the Sith have sought nothing but power. It's even part of their code: "...Through Power I gain Victory. Through Victory my chains are Broken. The Force shall free me." To them, the Force isn't something to understand but to control and to twist to one's own benefit. And this extends to the Star Wars: Episode I - The Phantom Menace, fans have believed that the Rule of Two refers to only two Sith in existence at once - but in actuality, the rule means there are two Dark Lords of the Sith; a master and apprentice to rule over the dark side of the Force.
Of course, it wouldn't be Star Wars if there wasn't a contradiction to this point somewhere in Legends. Years before Disney acquired Lucasfilm and relegated the Expanded Universe as Legends, there were a few stories in which Jedi Lord was used by people who guarded worlds outside of the Republic's domain, and so the citizens of those planets revered them as royals. Again, it was a non-canon story and the term Jedi Lord isn't used in canon. Overall, the Jedi have fancied themselves as Knights while the Sith see themselves as Lords.
