In public-key cryptography - one of the basis of cryptocurrency, digital keys are generated from a large random number through a cryptograhic key generation program to produce a private key and public key. In such a system, anyone can encrypt a message using the receiver's public key, but that encrypted message can only be decrypted with the receiver's private key.
Public keys can be disseminated freely as the receving address for your cryptocurrency.
It is a bullish signal in technical candlestick pattern by comparing two lines of short-term moving average and long-term average. It is a golden cross when the short term moving average broke its long-term moving average.