I am having a problem with understanding Stanza's in a poem. The following poem I need to know how does the second stanza build upon the first stanza and how does the third stanza build up on the first and second stanza's?

Stanza 1 - Twinkle, Twinkle, little star?
How I wonder what you are,
Up above the world so high,
Like a diamond in the sky

Stanza 2 - When the glrious sun is set,
When the grass with dew is wet,
Then you show your little light,
Twinkle, Twinkle all the night.

Stanza 3 - In the dark-blue sky you keep,
And often through my curtains peep,
For the never shut your eye,
Till the sun is in the sky.

Stanza 4 - As your bright and tiny spark
GUides the traveller in the dark,
Though I know now what you are,
Twinkle, Twinkle, litle star?