Shinobi are those who sacrifice all for the sake of their village. Their lives are usually dedicated to doing many missions for the sake and safety of their Kage, fellow Shinobi, as well as their common citizens. While most Shinobi work from the light, taking orders and missions from either a Jonin team leader or a higher official like the Kage themselves, some Shinobi operate from the shadows. Doing what needs to be done for the sake of their village, but usually entailing the grimmer work that most Shinobi either could not/would not do. There are also rouge Shinobi, who claim no land and are usually wanted for crimes or betrayal against their home villages.
Chakra is one's inner, almost spiritual-like energy. While most people are unable to tap into this, the Shinobi, when properly trained, is capable of all kinds of unbelievable things by molding their chakra and focusing it. Common examples of this are Shinobi's performing Ninjutsu techniques, focusing chakra into limbs to add power to Taijutsu attacks, sending small, concentrated amounts of chakra to their hands and feet to walk on water or walk up vertical surfaces, and also sending their chakra into others to disrupt or perform Genjutsu manipulating their opponents/comrades own inner chakra network.
The Basic 5 elements are:
*Lighting
*Earth
*Water
*Wind
*Fire
Ninjutsu is defined as 'Ninja techniques' and usually requires hand seals, as well as molded chakra to be performed. This is not always true, as some Shinobi have been shown to perforn techniques without the need for handsigns(Like Hashirama's wood techniques for example). Unlike Genjutsu, Ninjutsu is very real, and is usually used in conjunction with 1 of the 5 basic elements
sorry if that wasn't detailed enough...I swear I'm a quick study