A typical pattern on this site might look something like this:
R1: 5sc in magic circle (5)
R2: [2in1] x5 (10)
R3: [1sc, 2in1] x5 (15)
R4-5: 2 rounds only sc (15)
R6: [1sc, 2to1] x5 (10)
First of all, here are the abbreviations
R = Round, and indicates what round you are on
sc = Single crochet
2in1 = increasing, or using two sc in one hoop
2to1 = decreasing, or making two sc become one
Tutorials on all these techniques can be found here
When you understand the abbreviations, you can move on to understanding the structure of the pattern.
The patterns on this site are based on how many times you repeat what is in the brackets . How many times you repeat it is indicated by what is after the x (symbol for times in math). So, x5 means that you do what is inside the brackets  5 times. For example, in R3, you are supposed to do [1sc, 2in1] x5. In other words, Round 3 could be written out like this: “R3: 1sc, 2in1, 1sc, 2in1, 1sc, 2in1, 1sc, 2in1, 1sc, 2in1 (15)” instead.
The number inside the other brackets () show how many hoops should be in your ring after each round. So for example. After Round 1, you have 5 hoops in the ring because you have done 5 sc in the magic ring. In Round 2 you crochet 2in1 5 times, meaning that you increase with 5 more hoops that round compared to the last. So after round 2, there is 10 hoops in the ring = (10)
In Round 4 and 5 you are only doing sc, meaning there is no increasing or decreasing. One round of sc is 15 sc, so two rounds is 30.
If anything is unclear or you need help, please don’t hesitate to contact us, we will reply as quickly as we can and are always happy to help out fellow crocheters!