What is it?
Delta-V (Δv) represents the maximum change in velocity a rocket can achieve.
It is a measure of the rocket’s capability to perform maneuvers such as launching, orbiting, or landing.
Importance
Delta-V (Δv) is crutial for any mission, since you need a certain amount of it to perform the mission, therefor it is calculated beforehand
How to Calculate Delta-V (Δv)
The equation used to calcute Delta-V is:
Δv = vₑ * ln (m₀/mₜ)
in which vₑ is the exhaust Velocity, m₀ is the initial mass (e.g a fully fuled rocket) and mₜ being the final mass (e.g a half empty rocket)
This has been an MIS Blog Post.