Create invoices for your clients. Use can choose between several templates. One invoice is always cerated for one client, where you decide which projects will be included. You can also select a timeframe (limiting the timesheet entries) which will be used for generating the invocie.
In most cases you do not want to use an existing template. But you can modifiy existing or create new templates for you and your company.
There are also existing templates to download that are shared with the community.