Costs are money that your company spent on any material (not work hours of employees) to realize a deliverable for a project.
To add costs to a deliverable, start a calculation and add the cost amount and sales amount.
Costs added to deliverables with time and material are automatically added to an invoice to the customer. Costs added to a deliverable with fixed price are not invoiced, but registered to keep track of the budget.
Costs is money spent by the company. Money that you spent as an employee can be registered as expenses in your personal menu.