Forum Side ans Block Options

[alfuzzy]

I noticed in the Admin Control Panel Area...if I go to Options...I see the "Forum Sidebar and Block Options".

I think I understand that with this option...sidebars or blocks can be created on the left or right side of forum pages. Then if the "create Forums blocks" link is clicked on (screenshot 1)...eventually we get a drop down menu to select which block type to create (screenshot 2).

Can someone please explain what each of these block options does? I sort of understand some of them...but not all:

- Activity Stream
- Custom HTML/PHP
- New Forum Posts
- Group Discussions
- Tag Cloud
- Forum Threads

Thank You