A phrase used colloquially to mean "bring to an end." Its origins lie in the literal act of bringing down the stage curtains at the end of a play or performance. This also occurs between acts so that sets can be changed, etc., but in the colloquial use, it implies a more final end.
By implication, the event so described should bring a bit of applause - either from respect (the end of a respected thespian's career) or relief (the retirement of a politician).