Ninja: Ninjas are some people who train, fight and use Jutsus. Only Ninjas can use Jutsus. Most of the people are Shinobi.
Chakra: Chakra is a kind of energy wich flows in the body. Ninjas can use Chakra to perform Jutsus.
Ninjutsu: Ninjutsu is category of Jutsus. Ninja Techniques are the most common. They are often performed with Hand Seals and use of Chakra.
Elements: There are 5 basic elements: Fire, Air, LIghtning, Earth, Water.
Elemental Ninjutsu: Elemental Ninjutsu is every technique which is performed with an Element. For example Rasengan is not an Elemental Ninjutsu because it is just chakra not combined with an Element.