What is stereochemistry?
The study of the spatial arrangement of atoms in molecules (including the study of chiral molecules).
What are chiral molecules?
A chiral molecule is a molecule that is not super-imposable onto its mirror image.
What are chiral centers?
A chiral center, also known as a stereocenter, is an 
hybridized carbon that is bonded to four different molecules.
What are meso compounds?
Any compound with a line of symmetry.