What's the point of realizing?

[Landshark <lndshark megsinet net>]

What exactly is the point of realizing a widget?

I've seen it done in a few places, but the one that confuses me is for a
window.  In testgtk, the create_toolbar function realizes the window it
creates.  I've never done this before and am wondering if I should be.

+--------------------------------------+--------------------------------+
| -Dave                                | // Name that OS                |
| lndshark@megsinet.net                | #include <slow_crap.h>         |
+--------------------------------------+ #include <more_crap.h>         |
|       Visit The Hate Page!!!         | slow_t main()                  |
| http://doombbs.ml.org/~lndshark/hate | {return blue_screen_of_fun();} |
+--------------------------------------+--------------------------------+