The most important "numbers" are the ones that show what the water that your fish are swimming in is like.
The first, ammonia, is a test of the amount of ammonia found in the wtaer. Ammonia gets in the water when your fish eliminate, left over food rots, dead plants decay, etc. Ammonia in the water is toxic to your fish - the more ammonia - the more toxic it is. Fish can tolerate ammonia in the water - some more than others, but it is never a good thing to have. A test for ammonia is usually an indicator chemical that is mixed with another chemical to react - showing a color which is "read" by comparing the color on a chart. You are striving, when cycling a tank, to have zero ammonia in the tank.
In the nitrogen cycle - what we mean when we refer to the "cycle of the tank", beneficial bacteria will take the ammonia that the fish put in the water, and, using oxygen, one type of bacteria processes it into nitrItes. The next type of bacteria processes those nitrItes into nitrAtes.
NitrItes are quite toxic to fish. They are invisible, odorless and the only way you can tell they are in your water is by using a test. You are striving for zero parts per million of nitrIte in your tank, also.
The final stage of the nitrogen cycle is the nitrAtes. Nitrates are, also in the water, and, also are invisible and odorless. Nitrates are fertilizer for algae. They also can have a detrimental effect on the goldfish. High nitrate values can cause a fish to flip upsidedown. A fish can tolerate a lot more nitrates in the water than ammonia or nitrites, though. Most people aim to keep the nitate values at 40ppm or under.
pH is the measure of the acidity or base of the water. It refers to the amount of free hydrogen ions in the water. Just know that it means how acid your water is. Goldfish can live in a very wide range of pH in the water. 7.0 is neutral - neither acid nor base. The higher readings are more base, the lower are more acid. A goldfish is comfortable in 7.0-8.6 pH. They can tolerate a bit lower and a bit higher easily. The beneficial bacteria that process the ammonia/nitrite in the water do better at about 7.6-8.4pH.
pH, too, can be tested with a water test.
There are dip tests - a strip of paper with some chemical pads on it - that you dip into your tank's water and compare the colors on the strip to some master chart to tell you your nitrite, nitrate, pH, kH, gH readings Ammonia is usually done on a different strip. You can also find drop test - using small test tubes in which you put a sample of the tank water and a counted number of chemical drops to produce a reading - a color to compare on a chart.
Does that help a bit?