Channels are chat rooms with useful features designed to increase communication and collaboration. For example, you can have a dedicated channel for the designers in your workspace to discuss design-related topics.
Type of channels
Channels can be made private or public. The list of channels that you are a part of can be found on the workspace sidebar.
Public channels
Public channels are open for all members of a Rocket.Chat workspace to join, and anything posted is searchable by all members. They are identified by: 
Public channels can be used to make it easy to find out what's going on with your team. New members can join a channel and read all the information previously shared by other users. Public conversations help you build your organization's knowledge base with minimal effort. For example, you can create a channel for a company department or to discuss a specific programming language.
Private channels
Private channels are closed channels. They are only visible to their members. Use private channels for sensitive, confidential subjects that are not open to all members. They are identified by: 
Private channels can be joined by invitation only. The administrator sets the permissions, determining who can invite others to the channel. By default, only administrators, room owners, and moderators can invite others to private rooms.
Channel security and permissions
The following channel options help you fine-tune the security of certain organization-wide channels. This ensures that only members with permission can send messages to the channels.
Read-only channels
Only users with the Post ReadOnly permission can send messages in Read-only channels. Read-only channels are most suitable for announcements and voting. To allow other users to react to messages in this channel, go to Channel info > Edit > Advanced settings and enable the Allow reacting option.
Broadcast channels
Like read-only channels, broadcast channels allow authorized users with the Post ReadOnly permission to write new messages while other users can reply to existing messages.
However, it differs from read-only channels in the following ways:
All messages have a reply button that redirects you to the sender's direct message (DM), replying to the message as a quote.
Users can’t react to messages.
Encrypted channels
Encrypted channels have end-to-end encryption enabled across all messages exchanged by the channel members. To learn more, see End to End Encryption.
Channel information
The room information screen gives detailed information about the current channel. These details include:
Channel Name: The channel's name and how users see the title and find the channel via search.
Topic: The topic is displayed next to the title on the channel header. It is a great way to provide more channel information.
Announcement: Announcements are highlighted in a bar under the channel header.
Description: The description of the channel.
Private: Indicates whether the channel is private or public.
Read Only: Indicates whether a channel is read-only.
Archived: Indicates if a channel is archived. Nobody can post messages on an archived channel; a channel search will not find that channel. Admins can find archived channels using the Directory.
Password to access: Protect the channel with a password that allows you to set the password. Users must enter the password to become a channel member if a channel is password-protected.
If a Retention Policy is active on this channel, a red warning box appears stating when messages or files are deleted.
Learn about the Rocket.Chat room roles here.
About the general channel
When workspace administrators first log in to the workspace, the general channel is automatically created, and all users are added to it by default. Administrators can manage the channel settings or delete it, similar to any other channel. For more information, see Manage Channels and Channel Actions.