Active means that anyone looking to hire can search and see your profile and could potentially invite you for an interview. Good for those who need a job quickly.
Hidden means that your profile is not searchable and remains hidden from view. This means that only the jobs that you apply for will see your profile. Good if you don’t want your boss to know that you are looking for another job.
When you start a new job, change your profile to ‘hidden’ to avoid receiving job invites.