When you register at Hubzilla you are presented with a choice of channel roles. There are
[list]
[*] social channels with varying privacy settings
[*] forums with varying privacy settings
[*] feed channels
[*] a soap box function for announcement only channels
[*] group repositories
[/list]
The docs explain the basics about what is what, but I was always missing  a tabled overview. So I created one.

When you register at Hubzilla you are presented with a choice of channel roles. There are

• social channels with varying privacy settings
  
• forums with varying privacy settings
  
• feed channels
  
• a soap box function for announcement only channels
  
• group repositories
  

The docs explain the basics about what is what, but I was always missing  a tabled overview. So I created one.

And this is from the documentation at /help/en/member/member_guide#Account_Permission_Roles
Social - Federation
This is a special setting that you do need only if you want to use federation to other networks using for example ActivityPub or Diaspora*. Please note: With this setting you cannot benefit from the advanced privacy capabilities Hubzilla usually has to offer, and you will not be able to use nomadic identities!
Social - Mostly Public
The channel is a typical social networking profile. By default posts and published items are public, but one can over-ride this when creating the item and restrict it. You are listed in the directory. Your online presence and connections are visible to others.
Social - Restricted
By default all posts and published items are sent to your 'Friends' privacy group and not made public. New friends are added to this privacy group. You can over-ride this and create a public post or published item if you desire. You are listed in the directory. Your online presence (for chat) and your connections (friends) are visible to your profile viewers.
Social - Private
By default all posts and published items are sent to your 'Friends' privacy group. New friends are added to this privacy group. You can over-ride this and create a public post or public item if you desire. You are NOT listed in the directory. Only your connections can see your other connections. Your online presence is hidden.

Forum - Mostly Public
The channel is a typical forum. By default posts and published items are public. Members may post by @mention+ or wall-to-wall post. Posting photos and other published items is blocked. The channel is visible in the directory. Members are added automatically.
Forum - Restricted
By default all posts and published items are sent to the channel's 'Friends' privacy group. New friends are added to this privacy group. Members may post by @mention+ or wall-to-wall post, but posts and replies may also be seen by other receipients of the top-level post who are not members. The channel is visible in the directory. Members must be manually added by the forum owner.
Forum - Private
By default all posts and published items are sent to your 'Friends' privacy group. New friends are added to this privacy group. The owner can over-ride this and create a public post or public item if desired. Members cannot. You are NOT listed in the directory. Only your connections can see your other connections. Your online presence is hidden. Members must be manually added by the forum owner. Posting by @mention+ is disabled. Posts can only be made via wall-to-wall posts, and sent to members of the 'Friends' privacy group. They are not publicly visible.  

Feed - Mostly Public
Similiar to Social - Mostly Public, but tailored for RSS feed sources. Items may be freely republished and sourced. Online presence is meaningless, therefore hidden. New connections are automatically approved.  
Feed - Restricted
Not listed in directory. Online presence is meaningless, therefore hidden. Feed is published only to members of the 'Friends' privacy group. New connections are automatically added to this privacy group. Members must be manually approved by the channel owner.

Celebrity/Soapbox
Listed in directory. Communications are by default public. Online presence is hidden. No commenting or feedback of any form is allowed, though connections have the ability to "like" your profile.

Group Repository
A public forum which allows members to post files/photos/webpages.