---
meta:
title: "Concepts"
parentTitle: "Comments"
description: "Learn about threads and comments"
---
A quick overview of the concepts used in Liveblocks Comments.
## Threads
In Liveblocks Comments, everything revolves around _threads_. In each
[multiplayer room](/docs/concepts/how-liveblocks-works#Rooms) you can create a
number of threads. Each individual thread contains a list of _comments_ written
by your users.
Threads can be retrieved by
[a React hook](/docs/ready-made-features/comments/hooks#threads-hook) or
[on your server](/docs/api-reference/liveblocks-node#get-rooms-roomId-threads).
Here’s an example of a thread object.
```ts
{
type: "thread",
id: "th_sf8s6sh...",
roomId: "my-room-id",
createdAt: Date ,
resolved: false,
comments: [
// A list of comments in the thread
// ...
],
metadata: {
// Your custom thread metadata
// ...
},
}
```
Threads can store
[custom metadata](/docs/ready-made-features/comments/metadata), which is helpful
for integrating them into your product.
## Comments
Each comment is created by a user, referenced by their
[user ID](/docs/ready-made-features/comments/users-and-mentions), and is part of
a thread. The first comment in a thread is displayed at the top.
Here’s an example of a single comment inside a thread object.
```ts highlight="8-24"
{
type: "thread",
id: "th_sf8s6sh...",
roomId: "my-room-id",
createdAt: Date ,
resolved: false,
comments: [
{
type: "comment",
threadId: "th_sf8s6sh...",
id: "cm_agH76a...",
roomId: "my-room-id",
userId: "alicia@example.com",
createdAt: Date ,
editedAt: Date ,
body: {
// The comment's text in `CommentBody` format
// ...
},
metadata: {
// Your custom comment metadata
// ...
},
},
// Other comments in the thread
// ...
],
metadata: {
// Your custom thread metadata
// ...
},
}
```
A comment’s `body` is in a custom `CommentBody` format, though you most likely
won’t need to use this, as we render it in React for you. We also provide a
number of functions that allow you to easily
[convert a comment’s body into Markdown, HTML, or plain text](/docs/api-reference/liveblocks-node#stringify-comment-body),
which is especially helpful for creating email notifications.
Similarly to threads, comments can also store
[custom metadata](/docs/ready-made-features/comments/metadata), which is helpful
for integrating them into your product.
### Deleted comments
Deleting a comment doesn’t remove the comment object from the thread, instead
the `comment.body` property is removed, and a `comment.deletedAt` property is
added, which contains the deletion time. This allows you to handle the deleted
comment in whichever way you see fit, for example you may like to create a
“message deleted” placeholder for the comment. Alternatively, the comment can be
hidden completely.
A thread is only deleted after all its comments have been deleted.
---
For an overview of all available documentation, see [/llms.txt](/llms.txt).