Domain Name is the name of the website.
tutorialsinhand is the domain name of this website.
Using the domain name anyone can access your website.
You need to type on web browser 'www.yourdomainname.com' and it will take you to the website.
Every computer connected to the network has unique IP address using which one can access theose computers. But IP address is a series of numbers (logical address) like 192.168.43.170 which is difficult to remember. So each IP is given a domain name which can be easily remembered.
When someone types the domain name then DNS server finds out the IP address of the domain name that you eneted and points you to that website.