Here's the poem, in the original with, I believe, the original title, with notes and source included:

On the Life of Man          
Sir Walter Ralegh


What is our life? a play of passion,
Our mirth the musicke of division,
Our mothers wombes the tyring houses be,
When we are drest for this short Comedy,
Heaven the Judicious sharpe spector is,                  5
That sits and markes still who doth act amisse,
Our graves that hide us from the searching Sun,
Are like drawne curtaynes when the play is done,
Thus march we playing to our latest rest,
Onely we dye in earnest, that's no Jest.  

[AJ Notes:

musicke of division,, the entr'acte, the music that marked
            the division between acts.
tyring houses, on the Elizabethan stage, the 'tiring house',
            from "attiring house" was the room where the actors
            got dressed before a performance.
spector, spectator, with a play on 'spectre'.
still, always, ever.
latest, last.]

Source:
The Anchor Anthology of Sixteenth-Century Verse.
Richard S. Sylvester, Ed.
Garden City, NY: Anchor Press, 1974. 341.

The poem compares life to participating in a play.  In short, the speaker writes that:

• our life=a play that's passionate
• our laughter=the music played between acts of a play
• our mother's wombs=the place where we get dressed to prepare for the short life that is a comedy
• heaven=a sharp audience that corrects us when we behave badly
• graves=that which hides us from the heat of the sun (life's difficulties?), and is like the drawing of a curtain when a play is over
• this is how we march toward our death, and death is serious, not funny

Thus, life is a comedy, to the speaker, but death is not. I'll leave it to you to draw the meanings from the metaphors.