In ManicTime tags are used to track work. TimeSheet is a view optimized just for tags, which allows you to generate different work reports.
Lets look at how it works. For example lets say these are my tags for the week:

For the first report lets just set the date range and click Generate report. This is what I get:

From this view I can clearly see that I worked on Client 1, Project 1, Testing on Monday, Tuesday and Friday, a total of 16hrs.
You probably noticed that all I only worked for Client 1. Now lets say our boss asks us for a report showing just projects for Client 1, nothing else.

Group by

In ManicTime tags are separated by comma. So we could say that tag 'level 1, level 2, level 3' is three levels deep. In the sample data, second tags were always projects, so in the field Group by I can now choose Second level tags instead of All tags. This will produce the following output:

Grouping fields allow you to specify by what to group, before ManicTime starts adding up time.
You have an option to group by different fields. Given this tag:

Tag:"Tag 1, Tag 2, Tag 3, Tag 4"
Note:"Sample note" 
Start:"8/25/2011 10:00AM"
End:"8/25/2011 11:00AM"

following would be the output of different options:

• All tags - Tag 1, Tag 2, Tag 3, Tag 4
• First level tags - Tag 1
• Second level tags - Tag 2
• Third level tags - Tag 3
• Fourth level tags - Tag 4
• Note - Sample note
• Day - 25
• Month - 8
• Year - 2011
• Timeline - Beside local tags, TimeSheet can also be used to generate reports for AutoTags and server Tag timelines. This option is useful if you generate report from two or more timelines, where you need to see how much work came from one timeline and how much from the other.

Total by

By changing Total by field you are telling ManicTime that when it start adding time up, it should sum it by day, or by month...

Include notes

When include notes is checked, all the different notes will be appended to the end of the table, each in its own line. This is useful if for example you just want to see how much time you worked on a Project and all the notes you wrote during that time.

Select timeline

Select timeline field will show up if you have either Autotag timeline or established connection to a server. By default it will be hidden and it will work on local tag timeline data. When you have established connection to the server, server timelines will automatically appear in the listbox.