A mastery allows you to learn techniques of that nature. At level 10, you may pick your first Mastery. Subsequently, at level 50, you may pick your second.

There are 5 elemental masteries and 3 non-elemental masteries, out of these 8 masteries 3 have a village restricted second path.

Each mastery has strengths and weaknesses.

Masteries

Fire Elemental Mastery allows the ninja to learn Fire techniques that allow ninjas to dish out large amounts of damage to multiple ninjas.

Wind Elemental Mastery allows the ninja to learn Wind Techniques that are sharp, fast and deadly.

Lightning Elemental Mastery allows the ninja to learn Lightning Techniques that are high in damage and immobilizing.

Earth Elemental Mastery allows the ninja to learn Earth Techniques that have large area of effect and effectively control crowds.
Water elemental Mastery allows the ninja to learn Water Techniques. Water is a very balanced nature and as such can be useful in many situations.

Medical Mastery allows the ninja to learn Medical Techniques such as healing and reviving fainted ninjas, as well as harness the deadliness of poison.

Weapon Mastery allows the ninja to learn Weapon Techniques and gives them strong control over tools and blades, making them able to use things like Shurikens, Kunais, Swords in extraordinary ways.

Taijutsu Mastery allows the ninja to master hand-to-hand combat and learn Taijutsu Techniques, taking physical limitations to a new level.

                                                            Village restricted secondary paths for masteries

As a leaf village ninja, you have access to a style of Taijutsu called Gentle Fist Style. You can use Gentle Fist Techniques by learning Taijutsu Mastery and adding your mastery points to strengthen.

As a sand village ninja, you have access to a style of Wind techniques called Fan Style. You can use Fan Techniques by learning Wind Mastery and adding your mastery points to strengthen.

As a mist village ninja, you have access to a style of Water techniques called Bubble Style. You can use Bubble Techniques by learning Water Mastery and Adding your points to strengthen.