Explain instance and schema in database management system

instances and schema are similar to types and variables in programming languages

Schema: 

the overall design of a database is called database schema example, the database consists of information about a set of customers and accounts and the relationship between them it is analogous two variable among fitted type information in a program.

Types of schemas : 

• Physical schema: it is a database design at the physical level it is hidden below logical schema and can be changed easily without affecting application programs.
• Logical schema : it is database design at the logical level programmers conduct applications using logical schema it is by far the most important schema in terms on its effect on application program
• Subschema: it is schema at view level

Instance : 

it is the actual content of the database at a particular point in time it is analogous to the value of a variable