All 3 sciences will get you ready for Courses related to science/med at uni while the 3 humanities you have listed will set you up for business/law or what ever for uni. You dont need to have those to get in to your course, but it is recommended that you pick them as it will be easier for you later down the track.
Also, the names of those should be obvious as to what they will teach you lol
similar to what iRuler said. The three humanity subjects you generally learn about ways people are affected and affect you and science is basically the others. I hope what i am saying is getting across here.