Components of Tier system

What is business logic and database? What role do these play as components in software architecture? Is database the same thing as RAM in Single tier? How to differentitate these components in a single tier architecture?

@Prathima_Bose In the single-tier architecture, the disk will act as the database. RAM will represent the cache.

Please read this for business logic.

@Shivang quick question on single tier application. How can data security is highest in single tier applications? In single tier applications, one server has all the code including database and if that server is attacked, data is exposed as well as application. So could not understand this part which is in the course.

Looking forward for your response.