This is based on the idea that the person is new to running and he progresses. Not someone who goes from cycling to running and can run a 5k in 18 min first time running. In that case that person can skip phases because he already has training under his belt
Untrained
This persons just started running. Every run is a pr
Novice
This person runs for a quite a while and maybe did a few races. A novice can run even a marathon and is getting PRs quite easily, something called noob gains (untrained persons need less training to improve). Running became easier for this person and maybe he is starting to understand his speed and how long can he hold different paces. Most participants in races are here and most of them just want to finish the race. The novice is simply described as someone that can improve from any physical activity
Intermediate
This person runs for more than a year consistently at least. Goals are to improve and be better at running. This person usually follows structured programms. PRs don't come so easily anymore, usually requiring lot of training. If for a novice PRs come every week/month, for the intermediate PRs can come a few months between or longer since noob gains have stopped. Intermediates usually compete in races with themselfs but they aren't quite there yet to win major races. They can win small races and age groupings quite often though. The intermediate is simply described as someone that needs structured programs and more complexity to improve
Advanced
This persons runs for a few years. This is someone who is close to reaching their maximum genetic potential.They require a very specific training program to improve their performance and PRs come very rarely. This person is in the first lines at a race and is competing for the podium but their win is not guarantee
Elite
This person is very similar to advanced. This is someone who is close or has reached their maximum genetic potential. Unlike the advanced, this person is a favorite in races. These are the people that get BIB nr. 1 at races.