How would I check to see what map name was said?

Well, what you are trying to do there is add a table onto a string (which obviously wouldn't work).

A better way of doing it would be to use :sub(), which grabs a section of a string based on the arguments given.

For your example, do something like:

if msg:sub(0,4) == "load" then --if letters 0 to 4 are "load" then...
    local MapName = msg:sub(5) --Everything from letters 5+
end

You could also use the :lower() method to allow the player to use any case when saying it, so this would be a final code:

local admins ={"EmperorVolvax"} 
local gid = 1173040 
local gidranks = {255,105,104,103,102,101} 
local maps = {"sft", "obby", "sft"}
--Dont Mess with the Below --

function contains(list, element)
    for _, value in pairs(list) do
        if value == element then
            return true
        end
    end
end

game.Players.PlayerAdded:connect(function(Player)
    if contains(gidranks, Player:GetRankInGroup(gid)) then
        for _,v in pairs(admins) do
            Player.Chatted:connect(function(msg)
                if msg:lower():sub(0,4) == "load" then
                    for i,Map in pairs(maps) do
                        if Map:lower() == msg:lower():sub(5) then
                            --ChosenMap = Map
                            --PositionInTable = i
                        end
                    end
                end
            end)
        end
    end
end)

If you still don't understand, try this wiki page:

http://wiki.roblox.com/index.php?title=Function_dump/String_manipulation#string.sub