On a Job you can create Custom Fields to allow you to easily label or tag a job i.e. you may want to group together all your large website build or rebrand jobs.
Go to Jobs > chose the Job you want to tag > Custom
Setup custom fields
Go to Setup > System Setup > Jobs > Custom Fields
Click in the Field Name column and type in a name for that Custom Field
Click the drop down arrow in the Values For List field and click Edit
You can then edit this field by adding a list of items. Once finished click OK.
There are 15 customisable fields in total; once you've customised the fields they'll be available to use in the Job Custom area and can be searched from within any job by clicking on the 'Find' button.