Basically, supply and demand are part of orders block, supply and demand theory reflects a situation similar to support resistance by looking at economic laws when demand increases the price will rise, conversely if supply increases the price will fall. Between the two there is an equilibrium position which indicates a balance of supply and demand. Usually marked with a sideways market
Order Blocks are a strategy by large institutions to place orders in blocks by measuring movements designed to enter and exit the market. This is like the work of the smart money concept in trading. Like small pieces in a game of chess, players place pieces in certain positions to reinforce the game plan.