sleeve tattoo (or tattoo sleeve) is a large tattoo, or a collection of smaller tattoos, that has a unified theme, that covers most or all of a person's arm, 
What'd a sleeve tattoo?
sleeve tattoo has a unified theme, whereas an arm covered in tattoos may have many tattoos 
OK why he need for tattoo in the first place?
Tattooing has been practiced across the globe since at least Neolithic times, as evidenced by mummified preserved skin, ancient art
Wow! It really dates back!
sleeve" is a reference to the tattoo's size similarity in coverage to a long shirt sleeve on an article of clothing
So now do one remove tattoo?
removal has been performed with various tools since the start of tattooing.