In order to understand the variation you need to understand the basic genetic make up this is as follows:
In any one person there is 23 pairs of chromosomes (46) in total, the sex chromosomes come from both the mother and father. The mother always provides the X and father then either gives an X or Y which determines either Boy with a Y or girl with an X chromosome.
In turner syndrome the girl is missing part or all of the X chromosome meaning they have just one X chromosome.
There are a few variations of TS they are as follows:
Classic
This is where one of the X chromosomes is completely missing
Mosaic
This is where ontop of the normal x chromosome the second x chromosome is either partially missing or abnormal or in some cases not there at all or finally rarely both x chromosomes are present.
Ischromosome
This is where the arm of the 46th chromosome is either split partially or completely