What is convex region and what is something that is not a convex region? (in geometry)

Hi guys I was studying geometry and couldn't understand what convex region meant. I tried google and wikipedia but I still couldn't quite understand. If any of you guys can help me comprehend this concept in any way (giving me a link or explaining it) I would really appriciate it. p.s I don't have a strong math background. Highest math class I took was for my college graduation requirement for a science major. Thanks in advance.