Reading a sewing pattern can be challenging at first. Let's try to make it easier:
A pattern block usually consists of the body parts, sleeves (if there are any) and extra features.
Usually sewing patterns appear in half. That is because most clothes are symmetrical so both sides are the same and it is easier (and safer) to work in half the pattern.
For our example we will use the Womens Basic Bodice sewing pattern block
What is written on sewing patterns? The pattern making information:
1. The name of the pattern. It should be written in all pieces.
2. How many pieces the sewing pattern includes.
3. The name of each piece.
4. The fabric that the pattern is made for. That can be woven, knitted or both.
Cutting Information:
Usually patterns are cut in folded fabric. Fabric is folded parallel to the selvage.
Right sides facing inside.
Grainline: That is a straight line and is your mark on how to place the pattern on the fabric. Grainline is always parallel to the selvage.
Using the information written in our example: the Womens Basic Bodice sewing pattern block includes the following cutting info:
1.At the front piece, Cut 1 on fold. It means to cut the pattern on the fold of the fabric. It's one piece to be used unfolded.
2. At the back piece, Cut 2 mirrored. It means to cut pattern on folded fabric, so when you are done two mirrored pieces would be made.
3. At the sleeve piece, also Cut 2 mirrored.
Transfering the Sewing Pattern to the fabric:
Pin the patterns following the cutting info and draw around them. Use a soap, an erasable pen or anything that won't leave a permanent mark visible from the right side of the fabric.
Make sure you also transfer any mark like a notch, or a dart. At our example pattern, there are chest dart, waist darts, shoulder dart and also notches that meant to be paired in order to secure that the front part of the bodice is sewn with the front part of the sleeve pattern and the back part of the bodice with the back part of the sleeve. 
(2 notches for the front parts and 1 notch for the back parts).
That's the basic pattern and cutting info written on sewing patterns.