What is allostery and what are the differences between competitive and non competitive inhibitors?

Enzymes have an active site and allosteric sites. Allosteric sites regulate the activity of the enzyme.An allosteric enzyme could be- an allosteric activator which binds and stabilises the active form of the enzyme (so upregulates the activity)- or an allosteric inhibitor which binds and stabilises the INactive form of the enzyme (so downregulates the activity)Allosteric inhibitors are also called noncompetitive inhibitors as they bind to the allosteric site whereas competitive inhibitors bind to the active site. In other words, the competitive inhibitor competes with the substrate for the active site.