Some of the features that help business work smarter every day include:
Role based applications: Different users can be shared different applications, so they only see what they need to see, nothing more and nothing less.
Row-level Permission: Different users can be configured to see different records within a table (John can only see the contacts that he is assigned to).
Object-level Permissions: Different users can be configured to add, modify, delete or see objects
Field-level Permissions: Different users can only see certain fields of a given record