Unique Visitors- Individuals who visited your site during the report period. If someone visits more than once, they are counted only the first time they visit.

Visits - Number of times a visitor came to your site. If a visitor is idle longer than the idle-time limit, WebTrends assumes the visit was voluntarily terminated. If the visitor continues to browse your site after they reach the idle-time limit, a new visit is counted. The default idle-time limit is thirty minutes.