Confused! What are the differences between code first and code only?

I'm kind of confusing about these two term. Could someone have a bit explain these terms?

I know the one is lik开发者_JAVA百科e, that we define our POCO classes, and then create a class that has a set of DbSet which inherited from DbContext.

Code-only development and code-first development are the same thing, both are utilizing Entity Framework without a physical EDMX file, everything is handled in code.