What is polarity and how is it related to chromatography?

Chromatography is a rather large discipline in lab work. A simple chromatography example would be putting a spot of ink on a tissue and wetting it -the ink runs as the water 'spreads' along the tissue paper, because the paper 'attracts' it. Water is a polar liquid: it has a slight dipole moment. Look up "dipole moment".

Water (H-O-H) has it because electrons tend to stay closer to the heavier oxygen nucleus, and the two protons (hydrogen nuclei) tend to have a slight positive charge. So, a central moment, and two external moments, of charge, a dipole. Lots of chemicals also have -OH groups, ones that don't tend not to mix with ones that do, and so on. And there are a lot more polar 'groups' that organic molecules can have hanging off them.