Particles

Particles are a type of Entity in Minecraft; they are graphical effects. The particles always seem to "look" at the player and will usually dissapear after a short period of time

You can reduce the amount of particles visible in the Options menu.

Types of Particles
In Minecraft's code one can find a variety of particles. To help modders or for curious players below is displayed the types of particles and its real name shown on the game's code. Particles collide with solid blocks and are slowed down by cobwebs, but are unaffected by other entities. Each particle texture is 8x8 pixels.