Tracer - the back of the bullet is packed with a slow-burning pyrotechnic compound, kinda similar to the guts of a highway road flare. The heat of the burning powder from firing lights off a "starter cap" packed over the compound in the back of the bullet, getting the flare effect started, and the flare compound burns for a couple seconds (both during flight, and after landing)

Incendiary - the nose of the bullet contains an impact-sensitive compound designed to create a hot, short flash of combustion on impact with something hard enough to set it off.

Tracer usually won't light things like fuel tanks on fire, unless it lodges in the tank, still burning, and lights up the fumes. Tracer can start grass fires, or light pools or piles of flammables on fire if it comes to rest nearby the fuel while still burning.

Incendiary is designed to set things on fire, especially when piercing fuel tanks, or impacting flammable materials.