Here are a few definitions from the Google Analytics Glossary that I often refer to:
Bounce rate is the percentage of single-page visits or visits in which the person left your site from the entrance (landing) page.
If your bounce rate is significantly higher than 40%, it is a sign that the content or presentation of your page may be causing people to leave the website.
The first page that a user views during a session. This is also known as the ‘entrance page.’
See the ‘Top Landing Pages’ report to see where your visitors are entering from and which landing pages are most effective.
Google Analytics records a visitor as new when any page on your site has been accessed for the first time by a web browser. This is accomplished by setting a first-party cookie on that browser. Thus, new visitors are not identified by the personal information they provide on your site, but are rather uniquely identified by the web browser they used.
The “(no referral)” entry appears in various Referrals reports in the cases when the visitor to the site got there by typing the URL directly into the browser window or using a bookmark/favorite. In other words, the visitor did not click on a link to get to the site, so there was no referral, technically speaking.
A pageview is an instance of a page being loaded by a browser.
Google Analytics logs a pageview each time the tracking code is executed. This can be an HTML or similar page with tracking code being loaded by a browser, or a call to _trackPageview() to simulate a pageview.
A unique pageview, as seen in the Top Content report, aggregates pageviews that are generated by the same user during the same session. A unique view represents the number of sessions during which that page was viewed one or more times.
A Visitor is a construct designed to come as close as possible to defining the number of actual, distinct people who visited a website. There is of course no way to know if two people are sharing a computer from the website’s perspective, but a good visitor-tracking system can come close to the actual number. The most accurate visitor-tracking systems generally employ cookies to maintain tallies of distinct visitors.
The percentage of site exits that occurred from a page or set of pages.