Context: In the first 4 pages of Neukirch's text algebraic number theory, there are references to 'rational primes' and 'rational integers'. These come up in the context of finding all primes and units in $\Bbb{Z}[i]$.
What does this refer to?
A guess: A rational prime in $\Bbb{Z}[i]$ is a prime element in $\Bbb{Z}[i]$, which is also an element of $\Bbb Q$, rather than being, say, $1+i$ (which is prime, but not a rational number). 'Rational integer' is less clear to me though, since all integers are rational.
Question: What do the terms 'rational integer' and 'rational prime' actually mean.