"URL with WWW and URL without WWW" -Is there any difference between them?

It does not matter if you have www in the URL or not, as long as you use the same URL always. This must be happening probably because your server is set-up to redirect the http://www.shareprogrammingtips.com/ to http://shareprogrammingtips.com/.

This will make sure that all the pages will always come to http://shareprogrammingtips.com/ and also search engines would index your site as http://shareprogrammingtips.com/. If your site is accessible from both http://www.shareprogrammingtips.com/ and http://shareprogrammingtips.com/ then the search engines would index both versions of your site, but the page rank of your site will be divided between these 2 versions as for search engines both these sites are different sites.

In the past, every URL required the www. prefix (i.e. www.hello.com). Nowadays we have naked domains which don't require this prefix (i.e. hello.com). We still have many domains with the www. prefix for legacy reasons.

When a company wants to buy a domain name, they can buy it either with or without the prefix, or get both (for example, buy the naked domain and set-up the same domain with the www. prefix as sub-domain) and configure both to load the same website. There are technical reasons to chosing a domain with a www. prefix (allows for certain cookie blocking polices) or a naked domain (shorter url).

Usually, one of the two will be the canonical (real) domain, while the other will only redirect to the real domain. This redirect causes a delay but it's there for a reason.

If you code this redirect the right way, search engines will understand that both are the same website. Otherwise if you skip the redirect and point both domains to your files directly, search engines will think they are separate websites which will hurt your SEO (Search Engine Optimization).