# What does “A Target with Zero Doppler” Mean?

I have seen several references to target at zero Doppler and some simulations that command users to place a target at zero Doppler. I know that when a target is flying tangential to the signal the Doppler is zero (is this even true?) but I have no clues as to what the target being at zero doppler means.

$$F_{Doppler} = \frac{2 * F_{Transmit} * V_{Range} }{c}$$
$c$ being the Speed of light.
So, if the target's Radial Velocity is zero (not moving towards or away from the observer), $F_{Doppler}$ will also be zero.