When creating a project, there are two different project types you can chose from:
Billable: select this type for projects you can bill to your customers or to another organization in your company.
Non-Billable: select this type for internal initiatives that cannot be billed to another company, typically activities such as sales, pre-sales, meetings, internal trainings etc.
In terms of KPI reporting, please note that the while the "Productivity" KPI considers bookings on both billable and non-billable projects, the "Utilization" KPI only focus on Billable projects.
Note regarding "Time-Off" projects: such projects are useful to book "time-off slots", to represent your team’s vacation time, days off, illness and more. Such projects are handled via the Organization settings menu, accessible via your profile in the right hand corner.
When selecting time-off as project type, you will notice icons are proposed instead of colors. This helps you to immediately differentiate time-off projects from the others.