When you select an article the
current article buffer will be reused according to the value of
the variable gnus-single-article-buffer. If its
value is non-nil (the default) all articles reuse
the same article buffer. Else each group has its own article
buffer.
This implies that it's not possible to have more than one article buffer in a group at a time. But sometimes you might want to display all the latest emails from your mother, your father, your aunt, your uncle and your 17 cousins to coordinate the next christmas party.
That's where sticky articles come in handy. A sticky article buffer basically is a normal article buffer, but it won't be reused when you select another article. You can make an article sticky with:
To close a sticky article buffer you can use these commands:
To kill all sticky article buffers you can use: