Skew/skewed diagrams

I'm doing GCSE maths, and my coursework needs extending. I was told to get an A/A* I have to include some A-Level work in my work.

I've been told to search for A-Level Statistics, and especcially Skewed/Skew diagrams.

I really need help, as have been searching for these for ages! My teachers at school cannot help me. Please help!