[ajkjk]

Some people would call it a Kronecker delta instead, but imo they are exactly the same concept. The Kronecker delta is the indicator for a single value, like 1_{x=0}, while the Dirac delta is the indicator for a single 'dx' partition, divided by the width of the partition: δ(x) = 1_{0 in (x, x+dx)}/|dx| which is why integrating it ∫ δ(x) dx = ∫ 1_{0 in (x, x+dx)}/|dx| = ±1 (depending on the orientation of the integral). The Kronecker can sorta be viewed as the same thing but with dx=1, although that is kinda silly because usually you would intentionally evaluate it on a discrete measure anyway.

[TheOtherHobbes]

Dirac delta is infinitely tall. Kronecker delta has a height of 1. Both are infinitely thin. Much used in DSP.

[ajkjk]

I think you have missed my point. Both are defined to integrate to one, over different measures.