What is custom domain name ?
It is the URL(Uniform Resource Locator) you wish to use for your blog. It differs by your choice. but common extensions are like .in .com .org .pw .xyz .net it again depends upon your choice.
What will happen Later ?
Once you registered domain name of your choice you can use it to change your blog address (URL) which is hosted at blogger for this particular case. Assume it’s swapnilnakate.blogspot.in for this blog if I registered domain name as swapnilnakate.in and configured it. Then My blog address will be changed to swapnilnakate.in from swapnilnakate.blogspot.in.
Why to register domain name ?
If you register domain name for your blog it will be easy to remember your blog’s address to readers. also will be helpful to locate it. It is again be the simpler address if you choose to be.
Benefits of Having Registered Domain name
Your online identity will be protected and there you avoid confusion of being real you. There will always be atleast one identical person to you, so to avoid transfer of credits unknowingly/ misuse of your online presence you can go for domain name registration.
Where to register Domain name ?