This is legacy functionality, only available on accounts created before June 27 2016 and it is being deprecated on May 31st 2018.
Accounts that were created before April 2014, when we introduced the new BeepManager Incident alerting system, were migrated to BeepManager Light from the old alerting system. Accounts created after this date received the full BeepManager by default.
BeepManager Light is included by default in all legacy Pingdom plans. This alerting plan includes incidents and alert policies, but the latter only offers one assignment and an optional possibility to CC other users or alerting endpoints. On-duty schedules and maintenance are not included in this plan but you can look at demo versions of this.
BeepManager Pro provides full access to all Alerting functionality and is the default on all new Pingdom accounts. This plan allows for having additional users that can be invited, use them to manage incidents, scheduling and alerting. This is labeled simply as BeepManager throughout Pingdom.