Under All instances you will find all instances, completed and ongoing, that you have been involved in and for applications where you have at least a monitoring role. This is a preconfigured list, meaning it is configured automatically if the setting is selected. If you find this view overwhelming because their are many instances in your list, you can create a custom instance lists that is more suited to your individual needs. Read more on how to create your first list here.
If you do not see the All instances list and would like to, it will need to be turned on under Space settings. Only administrators have access to space settings. Administrators can turn standard lists on or off by going to the Space settings and scrolling down to List settings. Do not forget to select Save changes when you are complete. Choosing this setting will automatically generate the lists My tasks, All instances, and My started instances.
You can read more about Space settings here.