what is PlayerScore in data persistence?

So i'm going by the Roblox Wiki page (which isn't very descriptive on everything) but in this line of code

scoreKey = "PlayerScore"
 
game.Players.PlayerAdded:connect(function(player)
    if player:WaitForDataReady() then
	    -- create leaderboard
	    local ls = Instance.new("IntValue")
	    ls.Name = "leaderstats"
	    ls.Parent = player
 
	    --create the score stat
	    local score = Instance.new("IntValue")
	    score.Name = "Score"
	    score.Parent = ls
        score.Value = player:LoadNumber(scoreKey)
    end
end)
 
game.Players.PlayerRemoving:connect(function(player)
    if player:FindFirstChild("leaderstats") then
        player:SaveNumber(scoreKey, player.leaderstats.Score.Value)    
    end
end)

theres a variable named scoreKey = "PlayerScore"

what does scoreKey do for data persistence if anything at all? and does it need to be changed based off of the leaderstat??

Because I see that the leaderstat is named "Score". Do I change "PlayerScore" to "PlayerGold?" for my leaderstat which is "Gold"

No, unless you're making several values, although you should change it anyway as that's what its being saved as. Also, you really should consider using DataStore instead.