Ghidra is a Software Reverse Engineering (SRE) framework developed by the National Security Agency which was announced during the RSA 2019 conference. NSA has made the tool available as an open source software allowing and accepting contributions from the community. Its functionality is similar to other reverse engineering softwares such as IDA, Binary Ninja, Capstone etc. for analysing assembly level and malicious code like viruses or malwares.
Although the cyber security community is going to welcome the tool, the question of (“why”) NSA open sourcing such a tool will always remain unanswered.
You can find more about the tool on their website and GitHub.