Send incidences is an integration for sending over complete correlated Incidences with root-cause and impact information to create a ticket in your ITSM modules.
For all those ServiceNow users that have the ITOM module enabled we also send over all single events into the ITOM event table.
See here what the difference between correlated Dynatrace Problems/Incidences and events is:
Hello Kamal: There is no reason to do both at the same time when considering things from a ServiceNow perspective. If you send (from Dynatrace) Events into ITOM, your Alert Management Rules and related items in your ITOM workflows will evaluate whether or not to create an Incident from the alert. You may not want to create an incident each time there is a Dynatrace notification, or the event may correlate to an existing open Alert. With ITOM, you can also accept the notification of the Dynatrace problem closing and correlate that to the opening event in ITOM, effectively driving automation with regards to the closing of the ServiceNow alert and ServiceNow incident, for example. So if you have the opportunity, I would recommend going to ITOM only, and sending events for maximum flexibility on the ServiceNow side.