Container Forms "hold" subforms. Most subforms are based off multi-record tables, but they can also be based off other tables too.
When you set up a multi-record view form, you are asked if you'd also like to create a container. If you do not select to, you must put the subform on an existing form, so it can be seen. To build a container form later, create a New Form based on the Parent table.
Multi-Record Standard Forms Setup creates a Container form.