class : set of variables, constructors and methods. A class holds a name that it will be compiled as javac name.java and executed as java name (with JDK : java Developpement Kit compiler).

Concstructor: a function, with the same name as the class (name (...)), and that contains or not the declared variables. These variables will be used to construct the object of the class.

Method: a function or a procedure that manipulate the object. In this case, the method is satatic. If it doesn't deal with the object it is not static.

Variable: If a variable deals with the object, then it's a variable object. If not, it's then a class variable.

Field: All the separated members of the class holding data of the object or the class are called fields.

Instance: An istance is the fresh duilt object: the related sytax is: Constructor Instance = new Constructor(...); A class is instantiated when its constructor is called. Making an object is equivalent to create an instance of a class. Instance variable and instance methods are the variable and methods used when an instance is declared.

Modifiers (access modifiers): To set visibilty, a the name of class may be preceded by a modifier such as:
- public: visible from everywhere. In the directory (or package), where it is made, a class can be compiled and executed without the public modifier. The related fields followa the same rule.
- private: Fields (variables or methods) may be used only by an instance of the same class. This class which declares the variable or method,
- protected: Field are available to all subclasses of the class and all the classes in the same package.
Without any access modifier, the related class becomes a default class.
NB. main mehod must be always public. Class is either public
abstract. Fields are public, private or protected.

Type: Describes the kind of a variable or method like int, double, boolean, String, Object,.... A method (function) that returns nothing takes void as type.

extends: A class extends (inherits) from its super (mother) class, but it implements another class which is abstract ( with all fields abstract). A class can extends one class and implements many classes from the set called Interface. An abstarct class cannot be instantiated.

static: Field associated with a class rather than an object. Static fields are attached to a class, not an object.

final: Field that can not be changed. A class is declared as final if it can not be extended.