docs: add "What is Proxmox Backup"

docs/introduction.rst

@@ -3,7 +3,40 @@ Introduction
 
 This documentationm is written in :term:`reStructuredText` and formatted with :term:`Sphinx`.
 
-this is a test
+What is Proxmox Backup
+----------------------
+
+Proxmox Backup is an enterprise class client-server backup software,
+specially optimized for `Proxmox Virtual Environment`_ to backup
+:term:`virtual machine`\ s and :term:`container`\ s.
+
+
+Main features
+-------------
+
+:Proxmox VE: The `Proxmox Virtual Environment`_ is fully
+   supported. You can backup :term:`virtual machine`\ s and
+   :term:`container`\ s.
+
+:GUI: We provide a graphical, web based user interface.
+
+:Deduplication: Inkremental backup produces large amounts of duplicate
+   data. The deduplication layer removes that redundancy and makes
+   inkremental backup small and space efficient.
+
+:Data Integrity: The built in `SHA-256`_ checksum algorithm assures the
+   accuray and consistency of your backups.
+
+:Remote Sync: It is possible to efficently synchronize data to remote
+   sites. Only deltas containing new data are transfered.
+
+:Performance: The whole software stack is written in :term:`Rust`,
+   which provides high speed and memory efficiency.
+
+:Open Source: No secrets. You have access to the whole source tree.
+
+:Compression: Ultra fast `LZ4`_ compression is able to compress
+   several gigabytes of data per second.
 
 Why Backup?
 -----------
@@ -31,32 +64,6 @@ required by law.
 
 
 
-Features
---------
-
-:Proxmox VE: The `Proxmox Virtual Environment`_ is fully
-   supported. You can backup :term:`virtual machine`\ s and
-   :term:`container`\ s.
-
-:GUI: We provide a graphical, web based user interface.
-
-:Deduplication: Inkremental backup produces large amounts of duplicate
-   data. The deduplication layer removes that redundancy and makes
-   inkremental backup small and space efficient.
-
-:Data Integrity: The built in `SHA-256`_ checksum algorithm assures the
-   accuray and consistency of your backups.
-
-:Remote Sync: It is possible to efficently synchronize data to remote
-   sites. Only deltas containing new data are transfered.
-
-:Performance: The whole software stack is written in :term:`Rust`,
-   which provides high speed and memory efficiency.
-
-:Open Source: No secrets. You have access to the whole source tree.
-
-:Compression: Ultra fast `LZ4`_ compression is able to compress
-   several gigabytes of data per second.
 
 History
 -------