Object-Oriented Programming (OOP) is a way of structuring software around objects: self-contained units that hold both data and the actions that work on that data. Instead of one long list of instructions, the program becomes a set of objects that each know their own information and what they can do. A Customer object knows its name and orders; an Invoice object knows how to calculate its own total.
A helpful analogy is a set of LEGO bricks. Each brick is a finished, reliable unit with its own shape and connectors. You build something big by snapping bricks together, and you can swap one brick for another without rebuilding the whole model. OOP rests on a few ideas that make this possible, including encapsulation, which hides the messy internals of an object, and polymorphism, which lets different objects respond to the same instruction in their own way.
Objects usually come from a blueprint called a class. You write the Customer class once, then create thousands of customer objects from it, each with its own name and order history but the same shared behaviour. That reuse is a big part of the appeal on a large codebase.
Most popular business languages, like Java, C# and Python, support this style. It became the default for large applications because it maps neatly onto how people already think: in terms of things and what those things do. But it is not free of downsides. Overdoing inheritance or spreading logic across too many tiny objects can make a system harder to follow, not easier, so good OOP is as much about restraint as structure.
At TopDevs we lean on object-oriented design when a client system has many moving parts, because clear boundaries between objects make the code safer to extend years after the first version ships.
