Show or tell: what is it when it's at home?

[Poetry In Motion]

I would like to know people's thoughts on this frequently brought up angle in many critiques.

I am frankly often confused by the difference.  That is, I have hard time sometimes seeing the dividing line.  It seems like every poem is a telling.  I do understand the importance of showing, since images are sort of the blood of poetry.  

Maybe I'm the only person who doesn't quite get it.  Analysis is not one of my strong points.

Anyway, enlighten me!

Read into it. Read some literary criticism. Usually, the show don't tell phrase is simple: show me the window bouncing light from the glass instead of telling me that there is.