, 08:56 PM
Darksider and Dark Jedi are pretty much just colloquialisms, so which one you'd use to describe a dark side force user is more a matter of preference than anything.
But the Sith are a specific order of (dark side) force users tracing their history back to the Sith species and the banished Jedi who conquered them:
The Original Sith Empire:
7,000 Years Before the Battle of Yavin (which happened in Star Wars: Ep IV): Ajunta Pall and other banished Jedi enslave the Sith species - 5,000 BBY: Naga Sadow and the Empire are almost completely destroyed in the Great Hyperspace War.
The Lost Tribe of the Sith:
5,000 BBY: A warship of the Original Sith Empire crashes on the planet Kesh, the survivors conquer the planet but are stranded there - 40 Years After the Battle of Yavin: The Tribe regain space-flight and come into conflict with the Jedi.
The SW:TOR Sith Empire:
5,000 BBY: The Sith Emperor brings survivors of the Original Sith Empire to Dromund Kaas and begins rebuilding - ??? SW:TOR takes place about 3,640 BBY
The Brotherhood of the Sith:
4,000 BBY: Fallen Jedi Exar Kun and Ulic Qel-Droma become corrupted by Sith teachings and spirits and form an army of cultists, fallen Jedi and Mandalorians but are soon defeated/destroyed in the Great Sith War.
Revan and Malak's Sith Empire/Sith Triumvirate:
3,960 BBY: Jedi Revan and Malak are corrupted by the Mandalorian War and an encounter with the Sith Emperor and break away from the Republic, creating a new Sith Empire that goes to war with the Republic (The Jedi Civil War) - 3,955 BBY: The Empire is defeated in the Jedi Civil War, the last remnants of it are defeated in the Dark Wars (3,950 BBY).
New Sith Empire/Several Sith Warlords/Kingdoms/Cults:
Around 2,000 BBY: A fallen Jedi takes the name Darth Ruin and forms a new Sith Empire, after his death several fractured Sith kingdoms remain, fighting amongst themselves as well as the Republic/Jedi throughout the Republic Dark Ages - 1,010 BBY: The surviving Sith groups are reunited as the Brotherhood of Darkness.
The Brotherhood of Darkness:
1,010 BBY: Lord Kaan reunites or conquers the surviving Sith groups - 1,000 BBY: The Brotherhood is destroyed at the end of the Light and Darkness War, mainly due to the betrayal of Darth Bane.
The Order of the Sith Lords:
1,000 BBY: Darth Bane betrays the Brotherhood of Darkness and forms the Rule of Two: One Master, One Apprentice, allowing the Sith to survive in secret until Palpatine/Darth Sidious forms the Galactic Empire - 40 ABY: The last(?) Master/Apprentice pair of Sith Lords are defeated by the Jedi.
The One Sith:
Sometime between 4 ABY and 30 ABY: A fallen Jedi, corrupted in part by a renegade member of the Order of the Sith Lords, takes the name Darth Krayt and forms a new Sith order not limited to two members - 140 ABY: After conquering most of the galaxy between 120-130 ABY, the Sith are defeated at the end of the Second Imperial Civil War and the remaining members go underground to bide their time and recover.