How do you show Images via Tag?

Yes. I’ve read this:
http://nextgen-gallery.com/gallery-tags/
and
http://nextgen-gallery.com/albumtags/

but I don’t understand the example. He says

“Gallery tags
Since version 0.70 , you are able to show images in a gallery sorted by tags. If you enter the follow code in your post :
[ nggtags gallery=cologne,wordpress,… ]
You receive the followe images :
“

Can you tell me: Are “Cologne and WordPress” the names of the tags? Or are they the names of the galleries?

Same for here:

“Albumtags
Now is this a new way to sort galleries via the tag system. It only support the compact view . I used here the code:
[ nggtags album=WordPress,Cologne,Irland ]”

Is this showing all the images in the album named “WordPress” with the following tags of “Cologne and Irland”?

I know this seems like a basic question, but I’m having a *&%* of a time trying to show my images using the tag system.

Is the code:

[ nggtags album=album_name, tag1, tag2 ]

or, what is the code to make this happen? I’m about to tear my hair out over this simple thing!