The class is a software text. It is static, it exists independent of any execution. In non-OO distinct concepts Class is both a module, unit of software decomposition, but also a type. Uniform Type System. OO provides a simple uniform framework basic types are classes also and can partake in all OO games.
Good implementation avoids negative consequences from the decision to make all types classes.
Uniform access preserves autonomy of components by hiding implementation. Every operation of OO computation is relative to a certain object, the current instance at the time of the operation's execution. No software ever gets executed except as part of a routine call. Every call has a target. Hiding Full disclosure Restricting client Access How to build executable systems from individual classes.