# Architecture

Percona Backup for MongoDB consists of the following components:

* [`pbm-agent`](../reference/glossary.md#pbm-agent) is a process running on every `mongod` node within the cluster or within a replica set that performs backup and restore operations.

* [`pbm` CLI](../reference/glossary.md#pbm-cli) is a command-line utility that instructs `pbm-agents` to perform an operation.

* [PBM Control collections](../reference/glossary.md#pbm-control-collections) are special collections in MongoDB that store the configuration data and backup states. Both `pbm` CLI and `pbm-agent` use PBM Control collections to check backup status in MongoDB and communicate with each other.


* Remote backup storage is where Percona Backup for MongoDB saves backups. It can be either [an S3 compatible storage](../reference/glossary.md#S3-compatible-storage) or a filesystem-type storage.

The following diagram illustrates how Percona Backup for MongoDB components communicate with MongoDB.

![image](../_images/pbm-architecture.png){ align=center}