Tattoos are created by using special tools that use needles to insert permanent ink into the dermal layer of the skin. The ink changes the pigment of the skin where it is inserted, creating a work of art that stays on your skin for a long period of time.
The question many people ask is why don't tattoos fade or "heal" themselves over time? Tattoos are applied to the inner and not the outer layer of skin. A tattoo machine works by moving the needle up and down rapidly (around 50-150 times per second), piercing the outer layer of skin and injecting drops of the ink into the dermis with each puncture. The ink pigment particles are too large for the immune cells to destroy, so they get stuck in the dermis. Over the course of a few weeks after getting tattooed, the skin slowly repairs itself and while there is some initial loss of the ink during the healing process, ultimately with proper care the bulk of the ink is trapped in the layer between epidermis and dermis. It will generally remain there for the rest of your life as long as no major damage to the dermis region of body happens.
All tattoos will fade over time. One thing to keep in mind is that there are several places on your body where tattoos are most likely to fade at a rapid pace. Several areas have a tough time holding ink due to the types of skin on the body and the mobility of the area. Elbows are notoriously hard to tattoo and getting the ink to stay can be tough in the first place. Hand tattoos see almost constant sun exposure so they will fade. Finger and side of fingers are almost guaranteed to fade or fall out as soon as they heal.