please tell me the importance of Unique content in site
There are dozens of threads here explaining the importance of unique content. Do a search and if you have a specific question, either join an open discussion and ask it or create a thread that asks your SPECIFIC question. Just like any website, unique content is important to SitePoint as well and generic questions such as this one are not unique.
I encourage you to read our forum guidelines as well as our FAQs/rules to ensure that your future posts will not be closed or deleted.