Here you can see all kinds of information about the current channel. If you admin permissions, you can edit this information.
These are the channel info options:
Channel Name: The name of the channel, how users see the title and find the channel via search.
Topic: The topic shows next to the title on the channel header. Great for giving more info about the channel.
Announcement: Announcements post in a bar under the channel header.
Description: The description of the channel.
Private: Tells whether a channel is private, and can set the channel to private or public.
Read Only: Tells whether a channel is read-only, and toggles the read-only status on the channel. In read-only channels, only people with admin permissions can post messages. Good for announcements channels.
Archived: Tells if a channel is archived, and toggles the archived status of a channel. Nobody can post messages in an archived channel, and channel search will not find that channel.
Password: Tells whether a channel has a password and let you set the password. If a channel has a password, other users need to enter the password to become a member of the channel.