Help understanding this script?

I posted a question a while back on why my Level Up script wasn't working, and someone basically rewrote me a whole script from scratch, but didn't explain how it works.

I'm not sure how it works, and actually I don't think it does work. If someone could explain IN DETAIL how it works, especially the part I've highlighted in comments, I would really appreciate it. Thanks!

local xps = {0,3, 6, 10, 15, 20, 25, 30, 40, 50,
    65, 80, 95, 110, 125, 140, 155, 180, 210,
    250, 300, 350, 400, 450, 500, 575, 650, 725,
    825, 1000};
-- Just a list (divided by 100 to be smaller)

function experience()
    Player = game.Players.LocalPlayer;
    local xp = Player.Exp.Value;
    for level = 1, #xps do
        if xp >= xps[level] * 100 then --I'm not sure what the square brackets do here
            Player.leaderstats.PlayerLevel.Value = level; --I've never seen semicolons used in Rbx Lua?
        end
    end
    Player.HP.Value = 200 + 100 * Player.leaderstats.PlayerLevel.Value;
end

function health()
    Player.Character:WaitForChild("Humanoid").MaxHealth = Player.HP.Value
end

while true do --This was my attempt at looping the functions, I'm not sure if it works like this though.
	experience()
	health()
end

The experience function takes your experience value in a player and if the value is greater than or equal to one of the xps values, it makes the player's PlayerLevel the level it is equal to. The square brackets are a necessity of the for loop, simce it is iterating over the table xps. The function then sets the player's HP value to 200 + (100*the-player's-level-value).

I do not believe the semicolon is necessary.

The heath function sets the player's MaxHealth to the HP value, implying that you should cal, the health function after the experience function.

I would not suggest using a while loop to call the functions. Instead, you can do something like

game.Players.LocalPlayer.Exp.Changed:connect(function()
experience()
health()
end)

I believe this would call the two functions when your Exp value is changed. If you use a function like this, it causes a lot less lag then the while loop you have.

I hope this helped you! Good luck with your game!