How is the resistance level for a particular stock on the stock market, or for the index as a whole determined?

Generally people say resistance is at a point. It is an area. The area or price range where a stock gets selling supply or faces resistance from further rising, is the resistance.

Take Apple AAPL for instance. Stock resistance level was around 102 to 104 where it was getting strong resistance. Now it has crossed the resistance, and quoting at 105.

If you are from India, see the chart for State bank of india SBIN , where the stock is facing strong resistance in 2600 to 2650 area. Today, it is likely to close around that level having hit 2655 or so.