attempt to call table value even though I didn't attempt to actually call one(i think)?

In Lua, Objects are simply metadata, advanced forms of arrays built with metamethods (functions) to modify itself. Vector3 is one of these Instances.

For an easier understanding, let’s take a look at what the Vector3 constructor looks like:

local Vector3 = {} --// Raw Table
Vector3.__index = Vector3

Vector3.new = (function(x,y,z)
    local self = setmetatable({},Vector3)
    self.X = tonumber(x) or 0
    self.Y = tonumber(y) or 0
    self.Z = tonumber(z) or 0
    return self
end)

return Vector3

This is a highly complicated branch of tables known as Object Orientated Programming, so I won’t necessarily go into explaining how all of the code above works. But do notice one thing, Vector3 is assigned as an array. If we don’t call the .new() constructor to build our Vector data, we simply just end up passing a table.

The reason is because you put vector3 which supposed to be vector3.new

Part = script.Parent
go = true

while go do

repeat
    wait(0.5)
    Part.Position = Part.Position + Vector3.new(0.1,0,0)
until   Part.Position == Vector3.new(-54,7,-60) -- the error is on this line I think since this is line 9 
   end