Encapsulation
Encapsulation is one of the most important pillars of OOP. Encapsulation refers to the process of hiding or allowing access to state variables directly for changing their state. It refers to the pattern of declaring variables that cannot be accessed directly by clients and can only be modified using functions. This helps in constraint access to variables but, at the same time, allows enough access to class for taking action on it. Solidity provides multiple visibility modifiers such as  external, public, internal, and private that affects the visibility of state variables within the contract in which they are defined, inheriting child contracts or outside contracts.
