Classes in object-oriented programming are the fundamentals of encapsulation. Classes hold functionality that can be grouped to organize your code logically.
For instance, if you have functionality that helps you maintain employee information (name, address, ID, taxId, etc) and you have functionality that does payroll (create invoice, send invoice, transfer money) you would want to logically separate them into two different classes: Employee and Payroll (with the respective functionality) instead of having a mixture of functions lying around.
Classes are also the "blueprints" of instances when you fill out a "blueprint" with data. Employee is just a class, but when you create a new Employee with exact details, e.g.: johnDoe = Employee("John Doe", "12 Main Street, Dortmund, Germany", "ID1234567890", "TAX123456") then you have an instance. A new instance of the same class filled with different data will be different from the other instances.
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