A view is actually a composition of a table in the form of a predefined SQL query.
A view can contain all rows of a table or select rows from a table.SQL
creates the illusion of the view by giving the view a name like a table name and storing the definition of the view in the database.
When the view is queried, SQL Server
automatically determines which tables are affected by the query and references only those tables.
Views are used for security purpose in databases,views restricts the user from viewing certain column and rows means by using view we can apply the restriction on accessing the particular rows and columns for specific user.
Performance - since the joins already made and the tables are virtual, it's quicker to run a query on that dataset
It will decrease the complexity of your query.