Display list of updated software
#  yum list updates

To download and install all updates type the following command
#  yum update

List all installed packages
#  rpm  -qa
#  yum list installed
Find out if httpd package installed or not
#  rpm  -qa  |  grep  httpd*
#  yum list installed httpd

Check for and update specified packages
#  yum update [package-name-1]

Search for packages by name
#  yum list [package-name]
#  yum list [regex]
#  yum list httpd
#  yum list perl*

Install the specified packages [ RPM(s) ]
#  yum install [package-name-1]  [package-name-2]
#  yum install httpd*

Remove / Uninstall the specified packages [ RPM(s) ]
#  yum remove [package-name-1]  [package-name-2]
#  yum remove httpd*

Display the list of available packages

#  yum list all

Display list of group software
#  yum grouplist

Install all the default packages by group

Install all ‘Development Tools’ group packages
#  yum groupinstall “Development Tools”

Update all the default packages by group
#  yum groupupdate “Development Tools”

Remove all packages in a group
#  yum groupremove “Development Tools”

Install particular architecture package
#  yum install [package-name].[architecture]
#  yum install mysql*.i386

Display packages not installed via official RHN subscribed repos
{Show all packages not available via subscribed channels or repositories i.e. show packages installed via other repos}
#  yum list extras

Display what package provides the file

{You can easily find out what RPM package provides the file. For example find out what provides the /etc/passwd file}
#  yum whatprovides  /etc/passwd

You can use same command to list packages that satisfy dependencies
#  yum whatprovides  [dependency-1]  [dependency-2]

Refer yum command man page for more information
#  man yum