Bind-utils package is very helpful and it’s a collection of client side program includes the packages are nslookup, host and dig. If you execute these commands and getting below errors:

# dig centos.org
-bash: dig: command not found
# host redhat.com
-bash: host: command not found
#nslookup Ubuntu.com
-bash: nslookup: command not found

This error indicates to the bind-utils package not installed during Operating System installation. You need to install bind-utils package using yum command like below,
 
# yum install bind-utils

Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile

--> Running transaction check
---> Package bind-utils.x86_64 32:9.8.2-0.23.rc1.el6_5.1 will be installed
--> Finished Dependency Resolution

Dependencies Resolved
========================================================
 Package      Arch        Version      Repository                         Size
========================================================
Installing:   bind-utils    x86_64     32:9.8.2-0.23.rc1.el6_5.1    182 k

Transaction Summary
========================================================
Install       1 Package(s)

Total download size: 182 k
Installed size: 438 k
Is this ok [y/N]: y
Downloading Packages:
bind-utils-9.8.2-0.23.rc1.el6_5.1.x86_64.rpm                                                                                                     | 182 kB     00:00
...
Running Transaction
  Installing : 32:bind-utils-9.8.2-0.23.rc1.el6_5.1.x86_64                                                                                                          1/1
  Verifying  : 32:bind-utils-9.8.2-0.23.rc1.el6_5.1.x86_64                                                                                                          1/1
Installed:
  bind-utils.x86_64 32:9.8.2-0.23.rc1.el6_5.1

Complete!

Once installation has been finished, you can apply these commands again.

DIG :

Domain Information Groper (DIG) is a Flexible tool to interact with the DNS Name server and its clearly generate domain outputs.
 
# dig domain.com

; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.23.rc1.el6_5.1 <<>> thelinuxfaq.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 5327
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 0

;; QUESTION SECTION:
; Domain.com.               IN      A

;; ANSWER SECTION:
Domain.com.        3517    IN      A       192.168.0.1

;; AUTHORITY SECTION:
Domain.com.com.        86317   IN      NS      ns1.domain.com.
Domain.com.com.        86317   IN      NS      ns2.domain.com.

;; Query time: 1 msec
;; SERVER: 127.0.0.1#53(127.0.0.1)
;; WHEN: Tue Jun  3 23:05:44 2014
;; MSG SIZE  rcvd: 96

NSLOOKUP:

Nslookup is a program to query Internet domain name servers.
 
# nslookup Domain.com

Server:         127.0.0.1
Address:        127.0.0.1#53

Non-authoritative answer:
Name:   Domain.com
Address: 192.168.0.1

HOST :

 Host is a useful utility for getting DNS lookups used to convert names to IP addresses and vice versa. For example,
 
# host domain.com

domain has address 192.168.0.1
domain mail is handled by 0 Domain.com.

(Or)

# host -a domain.com

Trying "domain.com"
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 27770
;; flags: qr rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 2, ADDITIONAL: 3

;; QUESTION SECTION:
;domain.com.                      IN      ANY

;; ANSWER SECTION:
domain.com.               14386   IN      MX      0 domain.
domain.com.               14385   IN      A       192.168.0.1
domain.com.               86385   IN      NS      ns1.domain.com.
domain.com.               86385   IN      NS      ns2.domain.com.

;; AUTHORITY SECTION:
domain.com.              86385   IN      NS      ns2.domain.com.
domain.com.               86385   IN      NS      ns1.domain.com.

;; ADDITIONAL SECTION:
domain.               14385   IN      A       192.168.0.1
ns2.domain.com.    172785  IN      A       192.168.0.1
ns1.domain.com.    172785  IN      A       192.168.0.1
Received 182 bytes from 127.0.0.1#53 in 1 ms