What is the meaning of the following assembler-code line?

I´ve written the following code in C to let create assembler code from that and to learn something about assembler.

I start with a hello world of course, and in one line, there is following:

    mov DWORD PTR[esp], OFFSET FLAT:.LCO

and about LC0, it says:

    .string "Hello World!"
    .text
    .globl main
    .type main,@function

So, and I asked myself, what the meaning of line with OFFSET FLAT:.LCO ? Am I right, when I say, that something like a pointer which points to the string is given to esp? So that esp is now pointing to the string hello world, too?

Is that right? Because this would be logical.