vs
QUICK ANSWER
"Erre" is a form of "erre", a noun which is often translated as "r". "Ge" is a noun which is often translated as "g". Learn more about the difference between "ge" and "erre" below.
la ge()
A feminine noun is almost always used with feminine articles and adjectives (e.g., la mujer bonita, la luna llena).
la erre()
A feminine noun is almost always used with feminine articles and adjectives (e.g., la mujer bonita, la luna llena).