Saving up to get a sleeve tattoo one that takes up the whole arm
I love sleeve tattoo, ill probably get one soon. Are they popular? 
Yeah there is a difference between the sleeve tattoo and arm tattoo but both are popular
I do see a lot of people with sleeve tattoos! I'm guessing people have had them done throughout history? 
Yes they have and there are also half sleeves and quarter sleeves as well
I've seen a few celebrities with them, what else can you tell me about sleeve tattoos?
below the elbow. A sleeve implies complete tattoo coverage of a particular area, so a half sleeve is a tattoo that covers the entire upper or lower arm. A "quarter sleeve" usually covers the area of skin from the shoulder midway to the elbow.
Sleeve tattoos are a collaboration between a tattoo artist and customer to demonstrate a personal and unified artistic theme. Other times, a sleeve is created when a person has many smaller tattoos on their arm and later has them connected with background tattooing to form a sleeve
Sleeve tattoo
A 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, usually from shoulder to wrist.
There is a difference between an arm covered in tattoos and a sleeve tattoo. A sleeve tattoo has a unified theme, whereas an arm covered in tattoos may have many tattoos of different styles that does not have an overall unity.
The term "sleeve" is a reference