Schema and instance in DBMS

What is Schema?

 A database schema is the skeleton structure that represents the logical view of the entire database.
                                                                     (or)
                 The logical structure of the database is called as Database Schema.
                                                                     (or)
                        The overall design of the database is the database schema.

• It defines how the data is organized and how the relations among them are associated.
•  It formulates all the constraints that are to be applied on the data. 

example:

             STUDENT
                     SID                 /           SNAME               /              PHONE

What is Instance?

 The actual content of the database at a particular point in time.
                                             Or)
 The data stored in the database at any given time is an instance of the database