The .(dot) operator in Lua is used to invoke the method of an object, and it is a widely used operator in Lua.

The :(colon) operator in Lua is used when you want to pass an invisible parameter to the method of an object that you are calling.

when we use the colon(:) operator what actually happens is that instead of calling v3 = returnX:fun1(100, 1) what gets called is −
v3 = returnX:fun1(returnX, 100, 1) and hence we get the output as an address, and so in the second case when we call returnX:bar(10,11) the second argument will be 10 and that’s what we get.