When you graduate, whether or not during the academic year, you can choose from several options. You can decide to start working immediately, as an employee or as a self-employed person, or you can choose to continue your studies (possibly abroad).
If you have not found a job immediately after finishing your studies, it is best to register as a jobseeker with VDAB (residence in Flanders) or Actiris (residence in Brussels) as soon as possible. Every school-leaver needs to complete a 12-month vocational integration period and receive 2 positive evaluations of the efforts made before being able to apply for inclusion benefits. During your integration period, you must be available for the labour market and effectively look for work.
If you are registered as a job-seeker but decide later to go back to study, you can deregister without any consequences.