Yum  stands for Yellowdog Updater Modified, using this tool installing, removing, updating software packages on RHEL, CentOS, Fedora and etc. Linux distribution provide few commands for installation like, rpm, yum, apt-get, dpkg, etc.

1. yum install :

'yum install package-name'
this command will be install a software package automatically from a repository of your system. For example install vsftpd.

# yum install vsftpd

Now, the vsftpd packages getting from repository and ask  (Yes/No), [y/N]:y  If press 'y' packages downloaded and installed in your system.

If you dont want to ask any question and proceed automatically include with -y.
# yum install vsftpd -y

2. Yum group install :

To install all packages in the selected group for example use "web server"
# yum groupinstall "web server"

3.​Checking for updates:

Below comamnd want to check which installed packages on your system have updates available,
# yum check-update

audit.x86_64          2.4.1-5.el7              base
audit-libs.x86_64     2.4.1-5.el7              base
authconfig.x86_64     6.2.8-9.el7              base
avahi.x86_64          0.6.31-14.el7            base
avahi-glib.x86_64     0.6.31-14.el7            base

4. Updates :

If you have installed previous or older version, to update that packages or your basic system packages starts with 'yum update package-name'

The below command update basic system packages.
# yum update

To update a vsftpd package, run the following command,
# yum update vsftpd

To update related on security packages,
# yum update --security

5. Downgrade :

This sub-command downgrade a package to an earlier version
# yum downgrade vsftpd

6. Reinstall :

Yum command provide a option to reinstall current version, that sub command is 'reinstall'.
# yum reinstall vsftpd

Note : It will replace any deleted files.

7. How to remove packages:

if you want to uninstall packages (and possibly dependencies) from the system use sub command

'yum remove package-name' or 'yum erase package-name'
# yum remove vsftpd

# yum erase vsftpd

8. SWAP sub command,

At a single remove a package and install another one :

'yum swap remove-package  install-package'
# yum vsftpd proftpd

The above command remove vsftpd and install  proftpd package.