This is a simple cleaning process that removes tartar from the visible parts of your teeth. Not everyone has tartar on their teeth, so this is only done if necessary. It is part of your check-up.
A hygiene appointment is usually recommended to help with minor gum disease, or you may request an appointment to deal with stains.
Periodontal treatment is mostly used to treat advanced gum disease. Periodontal treatment is frequently carried out under local anaesthetic as it tends to be uncomfortable due to the need to clean out the gap between tooth and gum which can extend down to the roots of the tooth.