Jutsu can literally mean "Technique" or "Art". They are the basic fundamental of ninja itself. To perform any Justu, a ninja must learn to control and mix chakra together, the body and the spirit and the mind to manipulate and create the Jutsu.
Either by using up too much chakra or producing enough to perform a Jutsu. Chakra is the most important to correctly perform Jutsu. There are 5 elemental Justu...Earth, Fire, Wind, Water and Lightning and each require different amount of chakra to perform them.
Genjutsu (Illusionary Technique)-
Genjutsu is using the mind to create an Illusionary Image that is able to disrupted, impaled and paralyzed an enemy. The only way to counterattack an Illusionary Technique is to inflict pain. By inflicting pain, it is able to disrupt the bloodline flow to the brain and thus create an empty vision or erases the illusion.
Taijutsu (Hand-to-Hand Combat)-
Taijutsu is using the body to extract power and use it to damage an opponent. It require no hand seals but require mastery of chakra control and flow. The hands, body, and legs is all that is require to defend and attack an opponent. In Taijutsu, one can obtain enormous power and speed.
Ninjutsu (Ninja Technique)-
Ninjutsu is the usage of both the body and the mind. But usually anything that doesn't qualify as genjutsu (Illusionary Technique) or Taijutsu (Hand-to-Hand Combat Technique) will be consider Ninjutsu. Some ninjutsu require Hand Seals while other do not. There are many different form of ninjutsu but all ninjutsu require a person to use their mind to execute the Jutsu and the body to actually perform the Jutsu. It is more difficult but less stress on the body.
Fuuinjutsu (Sealing Technique)-
Fuuinjutsu require knowledge of seals and its foundation. Only high ranking ninja, Elite Jonin, Sannin, Kage and even Missing Ninja are able to perform sealing technique.
Kuchiyose no Jutsu (Summoning Technique)-
Kuchiyose no Jutsu is using the person's own blood to summon and control a certain animal. Some summon animals are able to talk while others cannot. Most commonly, summoning technique is use to summon animal(s) and even objects.
Kinjutsu (Forbidden Technique)-
Kinjutsu are forbidden technique that's either too powerful or dangerous for any ninja. They can only be use as the last resort. Forbidden Technique usually have consequences to the person performing the technique or someone else.
Kekkei Genkai (Bloodline Limit Techniques)-
The Kekkei Genkai are the abilities passed down from parent to child. These genetic inheritances grant the ninja unique abilities and physical traits not found anywhere else in the world.