As you get into bitcoin, you will no doubt check the price charts regularly.
When you switch to “candle view” on these price charts, you will see green and red candles, which represent Bitcoin price movements over a specific time frame that you can select from 1 hour to 1 month and beyond.
A green candle represents an increase in price from the start to the end of the time frame you select when viewing your price chart. The dirtiest turn of phrase you will sometimes see is “green dildo”, which means the same thing.
You will see people on Twitter referring to a green candle, usually on the hour, because people always get excited when the price goes up. A prolonged period of green candles could indicate a bull market.