Clone Technique (分身の術, Bunshin no Jutsu)
Ninjutsu, E-rank, Supplementary
Users: Uzumaki Naruto, Haruno Sakura, et al
Creating one's own after-image and confusing the enemy!!
A ninjutsu that creates an after-image of one's own body, without any substance. Since the clone itself doesn't have the ability to attack, and thus can only be used to confuse the enemy, it is mainly used in combination with other ninjutsu. It's a basic technique, but depending on one's ingenuity, it can be used effectively.
[picture of Sakura and two of her clones attacking Ino]
↑As Ino said, the "Clone Technique" is a ninjutsu that every ninja can use.
An elementary technique, even used as the Academy graduation exam
This technique, used in the graduation exam, is one of the ninjutsu Naruto is poor at. Because of it, he has failed the exam three times...

Shadow Clone Technique (影分身の術, Kage Bunshin no Jutsu)
Ninjutsu, B-rank, Supplementary
Users: Uzumaki Naruto, Hatake Kakashi, et al

A ninjutsu that creates a true copy of something. What makes it different from the normal "Clone Technique"* is that it creates a clone with substance, making them able to perform physical attacks. It's a high grade ninjutsu, allowing the clone to various techniques of the user. It used to be Naruto's worst skill, but nowadays it's his favourite by far. The way he uses it is also extraordinarily clever.
That shadow
It changes into yet another real body!!

[picture of Naruto attacking Zabuza from behind]
[picture of Naruto attacking Neji from the ground]
←↑By using the clone to attract the enemy's attention, the real body can appear from an unexpected place and launch an attack! This is the clever way the "Shadow Clone Technique" can be used.