N.B. I'm going to make the assumption you understand Delta V, if not, let us know. This map is used to plan your trip to other planets. We'll start small. If you look at the number in the middle of Kerbin, you'll see that it says 4500. This 4500 means that you'll need 4500 m/s Delta V (change in velocity) to get into orbit around Kerbin. From there, you need 860 m/s Delta V to intercept the Mun and you'll need a further 210 m/s Delta V to turn your intercept into an orbit (otherwise you'll just fling off the other side). To get to Gilly, for example, you'll need 4500 m/s to get into orbit, 950 m/s to escape Kerbin's SOI and intercept Kerbol (the Sun), 80 m/s to intercept Eve, (depending how you do the next part) 1310 m/s to orbit Eve and then 1650 m/s to intercept Gilly. Another 210 m/s to get into orbit and 35 m/s if you want to land. So all up, if you do it exactly as it says on table (there are other, more efficient ways), you'll need a ship capable of having 8735 m/s Delta V in order to land on Gilly. I hope this makes sense!