Schema or Structure can be defined in SQL

A schema is a collection of logical structures of data objects. A schema is associated with a database user and has the same name as that user. Each user have a single schema. Schema is mainly collection of objects can be created and manipulated with SQL.

In Sql if we look at the structure we first have a database for individual user and inside that database we have multiple objects means tables we can refer to the table as object

For ex:  Select * from dbo.student

dbo here is the Database Object which tells about the Schema we are using

Schema is like a container which contain objects or elements or tables whatever you want to say. So this container is like a class and everything inside this container is like an object