Neo-Traditional is a modern day spin on the traditional style of tattooing. It employs the use of various line weights and earthy bold colors, or black and grey.
Blackwork refers to tattooing consisting of dark imagery rendered in only rich, saturated black and greywash, often with stark constrating areas of white as well. It is also often done using dotwork shading.
Black & Grey Realism is exactly that. The use of black and greywash tattoo inks to create a photo-realistic image onto skin.