Please use the search function. There are numerous threads with lists of press release sites.

You don't know what a press release is but you have a website for SEO Services in Delhi? They must be hurtin for SEO if the SEO guys don't know what a press release is... Just sayin'

Press release is a technique to get more and more traffic on a particular website.

Press release is an effective SEO tool.

This is a few years old, but contains some good tips - 10 Ways to Make Press Releases More SEO Friendly

Press releases give good ranking to you keyword. Press releases are the advanced way to get good ranking to your site.

Press releases are meant to get your company name release to the public. It is sort of like news. They are beneficial for SEO as it can get you direct traffic and get your content syndicated which will in turn give you backlinks.

Press release is used to inform the user about launching particular products or anything if you want to inform anything to your use post Pr

Back links from PR sites are permanent.

Press Release is very power full part of link building in SEO, prlog.org good press release site ...

From wikipedia:
A press release, news release, media release, press statement or video release is a written or recorded communication directed at members of the news media for the purpose of announcing something ostensibly newsworthy.

From SEO point of view, the initial submission of the press release means backlinks. Upon syndication, the implication is more backlinks as the press release comes online on other press release sites.

I was Marketing Director for a company in the engery industry, and we used press releases a lot. We did real well with PR's but we had real news, and some of them made major industry magazines. We also got decent traffic from some online PR wires.