ATG BCC customization is not known to many and the term viewMapping is new to many.
Without proper documents,one gets stuck up on how to use it.
This blog contains the basic understanding of the viewMapping.
The terms you will come accross are ItemMapping ,ItemView, Item View Mapping, propertyViewMappings,propertyView,AttributeValues.
The view Mapping repository can be found in the dyn/admin.

As you might have seen in BCC when you navigate to the manage commerce assets and click on a particular asset( a category or a product or sku ) you see some properties in various tabs.
The tabs name, the properties to hide or display or to specify a particular length for a property can be done through the view Mapping.

You can create the ViewMapping in the ACC of your publishing server.
Open Acc -> go to Publishing -> go to viewMapping.

then you will see a list of itemMapping.
Each item descriptor is linked to a itemMapping. like for product the itemMapping name is DCS-UI product item Mapping,(the item mapping are for read only as well as edit mode).
which contains several itemViewMapping like the General,skus,Media,Advanced.These itemViewMapping contains the information for the ItemViews.
Item views specify the item view JSP fragment that renders a page of information for a particular asset type in a given mode.(while creating a new one, we generally select the default item View)
A propertyViewMapping identifies the propertyView used to render a specific property, or a component property if the property type is a collection.
A propertyView specifies the JSP fragment that renders a specific property in an itemView. It also identifies the property’s mode and data type.(here you can specify if you want to restrict the length of certain property or you want only numeric values to be entered for that property)