The most important measurements being used to indicate a bikes geometry are:

Length of the seat tube, this length will be measured between the bottom bracket and the upper side of the seat tube. This would be adjusted to your body length more often. This has no influence with the driving behaviour.

Length of the top tube, which will be measured between the head tube (at the handlebar) and the seat post. So you can’t know the exact length of the top tube. With an effective length of the top tube you’ll get an indication of the length of the cockpit. But the seat tube angle doesn’t have any influence in this case.
Head tube, this will be measured between the point where the fork enters your frame and the point where the first spacer upon your frame begins to appear. This has effect on your sitting position. The head tube can differ from 12cm for the small aeroframes to 25cm on the larger endurance frames.
Seat tube angle, you can measure this by drawing a straight line from your saddle straight through the bottom bracket to the ground. The seat tube angle helps you choosing the right sitting position. The bigger the frame, the smaller the seat tube angle, the further back you’ll be sitting.
Reach measures the length between the head tube and the bottom bracket if you would draw a line from the bottom bracket straight up. Based on the difference between the reach and the length of the top tube you’ll be able to define the aggressiveness of the sitting position of the road bike. A larger difference means you are able to sit further back, and with that you’ll have to bend your back more forward.
Stack, the stack measures the vertical height between the centre of the bottom bracket and the top of the head. With that you’ll see how high the handlebar will be. A short stack most of the time has a low sitting position as a result (aerogeometry).

Head tube angle, you measure this angle by drawing a straight line from the headtube to the ground, after which you’ll define the angle between that line and the ground. This particular angle is used as on of the most important indicators when it comes to the bikes driving and steering behaviour. A large angle is about 75 degrees and a small one is 70 degrees. A big angle is often used at aerobikes, because when you’re in a situation where you need to go through a bend you need to be able to steer very accurately and viable. A road bike with a much smaller angle feels less troubled in a bend and it gives you more trust and stability.
The wheelbase is a summation from the reach, the length of the chainstay and the head tube angle. An even easier way to measure it is to measure the scale between the axis of the front wheel and the rear wheel. With this calculation you can determine the bikes driving behaviour. Because of a longer wheelbase the bike will be much more stable than one with a shorter wheelbase. A bike containing a shorter wheelbase is more agile. Due to the influence of a large or small head tube angle and a long or short chainstay the driving behaviour may be different, while the length of the wheelbase can be even. Endurance road bikes often contain a longer wheelbase for more stability. 
Bottom brackets height, the height from the bottom bracket is measured by drawing a straight line between the ground and the bottom bracket. Because of different wheels the bottom brackets drop can be used instead of the height. The drop is a straight line between the axles and then measuring the height of the bottom bracket under or above this line. A lower bottom bracket creates a lower center of gravity on the bike. With endurance bikes you most likely see a higher number at the bottom bracket.

All of these measurements are parts to make your bikes geometry. Now you’ve read this article you know a bit more about what geometry you want to choose. I hope I helped you choosing your next race bike.