In finance, the term "close" can refer to several different concepts depending on the context. One of the most common uses of the term "close" is to refer to the closing price of a security, which is the final price at which it is traded on a particular day. The closing price is typically used as a reference point for measuring the performance of a security or market over time, and is often used to calculate key technical indicators like moving averages and trend lines.
The close can also refer to the end of a trading session or market day, which is the point at which trading in a particular market or exchange stops for the day. The close may be signaled by a bell or other audible signal, and is typically used as a benchmark for measuring the overall performance of the market or exchange during a particular trading day.

Daily close: This is the end of the trading day in a market, typically at the end of regular business hours. It is used to calculate daily price movements, and is often used by traders to make decisions on whether to enter or exit a market.
Weekly close: This is the end of a trading week, usually on a Friday. It is used to gauge the overall trend of the market for the week, and to make longer-term trading decisions based on the weekly price movements.
Monthly close: This is the end of a trading month, which is often used by investors and traders to make decisions on longer-term positions. Monthly closes are typically more significant than daily or weekly closes, as they can reflect broader market trends and shifts in investor sentiment over a longer period of time.

In the context of cryptocurrency, "close" usually refers to closing a trading position. A trading position is the buying or selling of a cryptocurrency with the intention of making a profit based on its price movements. When you open a trading position, you effectively "go long" or "go short" on a particular cryptocurrency. Going long means you expect the price to go up, while going short means you expect the price to go down.