What is the difference between SQL and APEX?

Can you clarify for me the fundamental differences between SQL and APEX? I'm trying to understand the distinction in terms of their purpose, functionality, and when they would be used in a development project. SQL is often associated with database management and querying, but how does APEX fit into the picture? Is it a replacement for SQL or does it work alongside it? I'm particularly interested in understanding the unique strengths and use cases of each technology.