In practice, they’re about the same. For example, in and and around my house I have 85 loci total. 60 loci are inside the house, and I added 25 outside my home, around the front of my house, the sides, and my backyard. I don’t really make a distinction, but I call the entire thing one memory “palace”. But it’s really just a long journey, starting in my master bathroom, then going to my master bedroom, etc. and ending in my backyard.
A journey is the route one takes to remember within a Memory Palace.
Memory Palaces are complete edifices a person uses in which a journey is made.
Example from History:
During the Renaissance, the stage of a Theater/Theatre would be used to make a journey in.
Although by itself the stage isn’t a “Palace” the entire Theater could, in theory, become a palace.
In Ancient Greek times, An empty gymnasium would be used as a memory palace, per se.
The point being that each locale would be used to remember.