Chakra- Chakra is the basic of all basics. It is like fuel for ninjas and is required to perform most ninja techniques, especially elemental techniques. Chakra also reflects how much energy one ninja has left. If a ninja has high chakra reserves, it means they have more room to perform techniques that are stronger or techniques in general.
Ninjutsu- It is ninja techniques. It ranges from simple ninjutsu techniques such as the substitution technique to a complex one like the rasengan. Most simpler ninjutsu are used to evade and dodge attacks that they wouldn't usually be able to. It mostly relies on hand signs, so the hand signs could mold the chakra in such a way that it would allow them to perform a specific technique.
Elemental Ninjutsu- Techniques that are like ninjutsu, but have one of the 5 elements with it. (fire earth water lightning wind.) These use nature transformation in the chakra so that they can change the nature of their chakra and shape manipulation to shape the expelled element. Some require hand signs to mold chakra and perform a specific technique while others done.