Summary
Member has, such as what Primary Membergroup the member is in. If the Member is in just a post-count based group, you will see the member's post-count based group. Administrators can also see the Hostname and IP address of the member.
Other information, like the date the Member registered, the last time a Member visited the forum, a notification shown to the Administrator if the member is banned, the current status of a member, their personal IM and email contact details, the member's gender, age and location along with their local time and what language they are using to browse the Forum, is also shown here. The email address is required, but a Member can choice to hide it from the other members of the forum.
At the bottom, the member's Signature along with three links are displayed. The first link, Show the last posts of this person, leads you to the same page as Show Posts, showing the posts made by the member. The second link, Show General Statistics for this member, leads you to the same page as Show Stats, showing some basic statistics of the member. Finally, Send this Member a personal message allows you to compose a Personal message to the Member (assuming you have proper permissions to send personal messages).
To the right is a column with the users Avatar and personal text, which is a quick one line text the Member can write whatever they would like it to say (appears under the Avatar in posts just as it does in the Profile summary page). Most of this information is not required to be filled out but is there to set a 'profile' of a member.