From b2evolution manual
This manual page is outdated. NEW PAGE: Stats Tab in b2evolution v5+.
 Select a blog
Choose which blog's statistics you want to look at. To see stats from across your whole installation, choose "None". In b2evolution 1.6+, each stats page contains a dynamically generated chart.
 Hit Summary
The Hit summary sub-tab shows a table of daily totals of each type of hit on your site.
See Global hits summary.
 Browser hits summary
The Browser hits sub-tab show a breakdown of the browser hits.
See Browser hits summary.
 Direct accesses
These are hits from people who came to your blog by direct access (either by typing the URL directly, or using a bookmark. Invalid (too short) referers are also listed here.)
A referal is when a reader comes to your blog by clicking a link from another site. For example, if b2evolution.net had a link on it pointing to your site, then each time a reader clicked on that link you would have a new referer stat from b2evolution.net. Checking this section is a good way to find out who is linking to you. The table at the top of the page shows the most recent referers. At the bottom of the page you'll find a table of the top referers.
Because b2evolution used to display referal statistics publically, many spammers started sending fake referals to b2evolution blogs (they're fake because their site doesn't really link to yours). The spammers were trying to sneak a link onto your site that links back to them, thereby raising their search engine ranking. Current installations of b2evolution don't display this information publically, but the spammers are still at it. The stats page includes a little Ban symbol in each row so you can quickly ban any spammy referals. You'll be taken to the antispam tab where you can delete all referals from that url and blacklist it so they can't add any more.
 Refering Searches
Some hits on your blog come from people who found you in a search engine. But what were they searching for when they found your blog? b2evolution keeps track of that, too. The refering searches tab shows you what search engine the hit came from, and what the reader had been searching for. Click on the text of the search term and you'll be taken to the results page that links to your blog. The right column shows which of your blog posts the reader ended up on.
"Top refering search engines" shows you which search engines are sending you the most traffic. And "Top Indexing Robots" shows which search engine robtos are spending the most time indexing your site.
Some people may read your blog by subscribing to your RSS feed in an RSS aggregator. It's basically web-based or desktop software that keeps track of all the sites a person wants to read, then notifies them of any updates and very often shows them the text of your post without them ever needing to visit your site. When an aggregation service scans your site for new updates, the hit is recorded here. Many services even report how many of their users are subscribing to your feed when they index your site.
 User Agents
Have you ever wondered what web browser and operating system your readers use? You can find those stats in the User Agents tab.
Goals allow you to track clicks on specific links and/or visits on specific pages.