Why is the average buy price different from the current market price?

Average buy price reflects what you actually paid, calculated across all your purchase transactions for that stock if you bought it in multiple lots at different prices, weighted by the quantity of each purchase. Current market price is simply where the stock is trading right now, and the two will only match by coincidence, since the market price moves continuously based on ongoing supply and demand, independent of your personal purchase history. If you bought 50 shares at ₹100 and later bought another 50 at ₹120, your average buy price becomes ₹110, and the current market price could be anywhere, above or below that average, depending purely on how the stock has moved since. This average price figure is what’s used to calculate your unrealised profit or loss on the holding, so you check it specifically when you want to know how a position is performing relative to what you’ve actually invested, rather than comparing the current price to just your most recent purchase.