The Calendar Overlays feature lets you create a combined view of your calendars by layering more calendars on top of the source calendar. For example, with Calendar Overlays you have one Calendar that you are currently looking at in your account. Any other Calendar that you have in your account can then be “overlaid” onto this Calendar. This means that you can have separate Calendars with different Events, but you can combine your Calendars as Calendar Overlays and see all of your Events at once.
Since a Calendar Overlay is just a Calendar in your account that is overlaid onto another Calendar in your account, you will need to change the name of your Calendar in order to change the name of the Calendar Overlay. Learn more about changing the name of your Calendar.