A Job Types feature allows the user to categorise jobs, tasks, variations, quotes and invoices using a custom set of labels. Job Types can be configured in Settings->Jobs Templates.
To edit the job's type, go to Jobs->Current Jobs.
On the first tab, select the Type from the Drop-down menu.
Back on the list view for jobs, invoices, etc, enable the Job Type column using the Columns selector in the top right.
The list can then be sorted by job type, with totals updating to items in the subset.