Monitoring voltage from a power supply

Hmm ok, now help me pick this code apart so I understand it lol.

#define VDIVIDE 2.8f

What does this accomplish? I don't understand the "f"

float result;

What does it mean to float something?

result = val / (1023.0f / 5.0f) * VDIVIDE;

Again, the "f" is throwing me off!!??