You don't say what processor and assembler you're using so it could mean anything. Different processors use different languages, and different assemblers for each processor implement the language slightly differently, so for the answer to mean anything it has to be in the context of a specific processor (or processor family) and assembler.

So it's entirely possible that dc.b means define constant byte, or possibly bytes, and that the particular assembler you're using allows you to define a series of bytes rather than making you do dc.b 'E' dc.b 'n' dc.b 't' etc, which would be really tedious.

org again depends on the processor and assembler, but often it's short for "origin" and defines what address the program should be compiled to.