Summarize this article:

Select from the different categories listed on the Yahoo! Groups main page found at www.groups.yahoo.com.  Categories include Business & Finance, Computers & Internet, Family & Home, Government & Politics, Hobbies & Crafts, Romance & Relationships, Schools & Education, and many more. Start looking for a group by clicking on any of these categories. Clicking on a group name will reveal a description of the group. If you know the name of the group you want to join, you can search for it.  Use the search box at the top of the Yahoo! Groups main page and type in the keyword(s) for the group you're looking for. Click the “Search Groups” button beside the search box to begin your search. You may need to try a few combinations of keywords until you find the correct group.

Summary:
Find a group by browsing. Find a group by searching.