Schema is the overall structure of a database. The schema comprises the Variable present in the database and also the instance of the database.
When we talk about Databases, Value is in the tables keeps on changing continuously. The change in values can occur as any insertion, deletion, or alteration on data happens. However we can say, the information present in a database at a particular moment is called its instance.
For a clear idea about Instance and schema, kindly refer to the image below