Job types are added to your job advert when they are created via the recruiter. When the applicant visits your job portal, it is possible to filter by job type.
When a job agent is created, you can filter by job type as well.
Therefore, it's a great idea to create job types in advance, to the extent possible, so that those who have created a job agent will be notified when a newly established job matches the job type they have shown an interest in.
Job types are created and edited in settings.