What is an Object in OOPS?

Object is an instance of a Class.
Object have state and behavior.
State of an Object can be stored in fields(Variables) & Behavior can be exposed using methods.

Real world example :
Dogs have state (name, color, breed, hungry) and behavior (barking, fetching, wagging tail).
Bicycles also have state (current gear, current pedal cadence, current speed) and behavior (changing gear, changing pedal cadence, applying brakes).

Code Example:

class Bicycles()
void changeGear(int newValue)
         gear = newValue;
public class Main()
Bicycles abc = new Bicycles();  //Object of a class
abc.changeGear(3);        //Behavior (changeGear method) exposed with state(variable "newValue" value)