what is the meaning of Press Releases and how can it works for seo and how can we do work with the Press Releases ?
You can put links into your press releases which help build backlinks. The press release gets picked up and you gain a backlink from any website that picks it up. The backlinks usually stay up for a few weeks before they start dropping off but you still keep some of them. I use PRWeb to distribute my PR's kind of expensive but usually generates a lot of links for me.
Your real value from those comes not just from the fact that it is a backlink but from where the backlink is coming from. If you can get a backlink from a well established or well recognized site such as a newspaper, .edu, .gov or other "high value" website the backlink is seen to have a lot more power in it than a link from something common like most directories or other new sites with little established value in search engines. It's also a great way to establish a brand name in the public's mind if you can get your company out there in an established area. Again, this really depends on what kind of press releases you're doing and who you're targeting, but there are some good ways to get out there and really target key markets to generate some high quality traffic.
SEO press releases can bring you first-page visibility for your keywords very quickly. Sometimes, you can take over multiple spots on the the first page of Google for your keywords.