When performing a sosl search, an s Object is an object that can be cached within the force dot com stage database which are not objects in the sense of occurrences of Apex classes. The objects are representations of data that has or will be persisted.
The object is a nonspecific abstract type that corresponds to any persisted object type. Each salesforce record is represented as Object before it is inserted into salesforce and they are stored in a sObject variable. sObject is returned when performing an sosl search.