A bull flag pattern is a chart pattern that occurs when a stock is in a strong uptrend. It is called a flag pattern because when you see it on a chart it looks like a flag on a pole and since we are in an uptrend it is considered a bullish flag.
You can watch to buy some altcoins when BTC sideway in this area. That ensures that if btc pumps up, you don't miss the train, and ensures you have usdt saved if btc dumps, you still have money to go to the market.