A small guide showing you what is Delta-V, or TWR or.... Other things.
Delta-V: The "Kilometers per galoon", for example, for get to orbit you need 6km/s of Delta-V, and for luna, you need 13km/s of Delta-v.
A vessel on the designer, showing the Delta-V on the vessel.
Apoapsis: The highest point of a trayectory/orbit.
Periapsis: The lowest point of an orbit.
An orbit, the orange triangle is Periapsis, the other, Apoapsis.
TWR: Thrust-Weight-Ratio, an equation that determines how much thrust you need to lift off the ground, if you have an TWR above 1, your rocket will start to go up.
SOI: Sphere Of Influence, the limit of gravitational attraction measured in kilometers, if you have an apoapsis higher than that, you will leave it's orbit, you will be on an escape trayectory.
A vessel on an escape trayectory.