In plain English
RSI asks whether recent weeks were more “up” or “down,” then squishes that into 0–100. Around 50 is balanced. Below 30 is oversold (lots of down weeks). Above 70 is overbought (lots of up weeks).
On bitcoin’s weekly clock, oversold has historically been a better one-year starting point than overbought. It can stay overbought in a roaring bull.