diff --git a/knowledge base/zypper.md b/knowledge base/zypper.md
index a17c186..cf5f3db 100644
--- a/knowledge base/zypper.md	
+++ b/knowledge base/zypper.md	
@@ -1,32 +1,153 @@
 # The Zypper package manager
 
-SUSE and openSUSE GNU/Linux's package management utility.
+SUSE and openSUSE GNU/Linux's package management utility and command-line interface to the ZYpp system management library (`libzypp`).
 
 ## Table of contents <!-- omit in toc -->
 
 1. [TL;DR](#tldr)
+1. [Concepts](#concepts)
 1. [Gotchas](#gotchas)
 1. [Further readings](#further-readings)
 
 ## TL;DR
 
+Default files:
+
+| Path                       | Description                                                 |
+| -------------------------- | ----------------------------------------------------------- |
+| `${HOME}/.zypper.conf`     | User configuration file for Zypper                          |
+| `/etc/zypp/zypper.conf`    | Global configuration file for Zypper                        |
+| `/etc/zypp/zypp.conf`      | Configuration file for `libzypp`                            |
+| `/etc/zypp/locks`          | Package lock definitions                                    |
+| `/etc/zypp/repos.d`        | Directory containing repository definition files (`*.repo`) |
+| `/etc/zypp/services.d`     | Directory containing service definition files (`*.service`) |
+| `/usr/lib/zypp/commands`   | Directory for zypper extensions                             |
+| `/var/cache/zypp/raw`      | Cache directory for downloaded, raw package metadata        |
+| `/var/cache/zypp/solv`     | Cache directory for pre-parsed package metadata (`*.solv`)  |
+| `/var/cache/zypp/RPMS`     | Cache directory for downloaded packages                     |
+| `/var/cache/zypp/packages` | Cache directory for installed packages                      |
+| `/var/log/zypper.log`      | Zypper's log file                                           |
+| `/var/log/zypp/history`    | Installation history log file                               |
+
+Command examples:
+
 ```sh
-# update the repositories
+# Update the package cache.
 zypper refresh
+zypper ref 'updates'
 
-# search for a package
-zypper search nmap
+# Search for resolvables.
+zypper search 'nmap'
+zypper se 'mariadb'
 
-# install a package
-zypper install parallel
+# Display detailed information about resolvables.
+zypper info 'workrave'
+zypper if -t 'patch' 'libzypp'
+zypper if -t 'pattern' 'lamp_server'
+
+# Install resolvables.
+zypper install 'parallel'
+zypper in --no-confirm 'https://prerelease.keybase.io/keybase_amd64.rpm'
+zypper in --no-recommends 'gv' 'virtualbox-ose=2.0.6' '/root/ansible.rpm'
+
+# Install resolvables from source.
+# The source packages *must* be available in the repositories one is using.
+zypper source-install -d 'dbus-1'
+zypper si 'dolphin-plugins'
+
+# Check the dependencies of *installed* packages are satisfied.
+zypper verify 'git-lfs'
+zypper ve 'virtualbox'
+
+# Uninstall resolvables.
+zypper remove 'code'
+zypper rm 'zfs'
+zypper in '!Firefox' '-htop'
+
+# List available updates.
+# By default, it shows only *installable* ones.
+zypper list-updates
+zypper lu --all
+
+# Update installed packages.
+zypper update
+zypper up 'vivaldi-stable'
+
+# List available patches.
+# By default, it shows only *applicable* ones.
+zypper list-patches
+zypper lp --all
+
+# Check whether there are applicable patches.
+zypper patch-check
+zypper pchk --with-optional
+
+# Apply patches.
+zypper patch
+
+# Perform a distribution upgrade.
+zypper dist-upgrade
+zypper dup --details --from 'factory' --from 'packman'
+
+
+# List currently defined repositories.
+zypper repos
+zypper rl -d
+
+# Add repositories.
+zypper addrepo --check --refresh --priority '90' \
+  'https://ftp.gwdg.de/pub/linux/misc/packman/suse/openSUSE_Tumbleweed/' \
+  'packman'
+zypper ar …
+
+# Remove repositories.
+zypper removerepo 'mozilla'
+zypper rr '3'
+
+# Rename repositories.
+zypper renamerepo 'firefox' 'mozilla'
+zypper nr '5' 'packman'
+
+# Modify repositories.
+zypper modifyrepo -er 'updates'
+zypper mr -da
+
+
+# Clean caches.
+zypper clean --metadata
+zypper clean --all 'packman'
+
+# Execute without user confirmation (non-interactively).
+zypper --non-interactive …
+
+# Clean up installed kernel packages.
+zypper purge-kernels --dry-run
 ```
 
+## Concepts
+
+The set of packages installed on a system is denoted as the _@System_ repository or _System Packages_.<br/>
+In contrast to normal repositories, @System provides packages that can only be deleted.
+
+Installed packages which do not belong to any available repository are denoted as _unwanted_, _orphaned_ or _dropped_.
+
+One can specify the location of packages or repositories using any type of URI supported by `libzypp` (e.g. local paths, ftp/https/other URI).<br/>
+In addition, Zypper accepts openSUSE Build Service repositories in the `addrepo` command in the form of `obs://project/platform` URI.
+
+Resource objects are called _resolvables_.<br/>
+They might be **packages**, **patches**, **patterns**, **products**, or basically any kind of object with dependencies to other objects managed by `libzypp`.
+
+If one does not request specific versions of resolvables during an action, Zypper's dependency solver will pick a _reasonable_ one automatically.
+
 ## Gotchas
 
-Zypper does not have for now a way to list the content of an installed package. Use [rpm] for this:
+Global options **must** be specified **before** the command name.<br/>
+Command-specific options **must** be specified **after** the command name.
+
+Zypper does not have for now a way to list **the content** of an **installed** package. Use [rpm] for this:
 
 ```sh
-sudo rpm --query --list ${PACKAGE_NAME}
+sudo rpm --query --list 'parallel'
 ```
 
 ## Further readings