Bounce rate is the precentage of visitors who enter your website and exit after a single page view (they never navigate to anther page on the site) Exit rate is the precentage of visitors who leave your website from a particular page. Theortically, exit rate should calculate visitors who leave the site on a particular page only if they have visited multiple pages in the site. In practice, that is not the case. GA reporting of exit rate incudes both single visits as well as multi page visit. So, exit rate includes bounce rate numbers in it.
kumar2, It's better to create a new thread then posting another question to the existing thread. Coming to your question, a visitor can have multiple visit. Its just like you visiting a shop multiple time. Here you are a single visitor making multiple visits. A visitor is identified on a website based on the cookie which the web analytics tool add into the visitor's browser.