Personally, I don't even really see the point in "Tagging" a roleplayer as Casual, or Hardcore, as was mentioned above by a few people. Having a list of different "Levels" of roleplaying could be a deterrent in it's own right. I believe the best description would simply be to make note on the two opposite ends of the spectrum, while mentioning all of the grey area inbetween. Simply because any "level" could have it's own tweaks based on the person in question. Perhaps they wish to roleplay every day, but they don't really want to get too deep into character development. Or perhaps they only wish to roleplay once in a blue moon, but when they do, they want to do so on a very deep level. There's really quite a few factors to tie in to be able to really nail down all of the different aspects of roleplay.
Again, that's just how I see it. Personal opinion.
But if I were to give rough definition of "core" levels?...
Light Roleplayer: A player who may enjoy a form of "No-strings-attached" roleplay. Tends to be out of character more than they are in-character, and generally do not participate in in-depth character development and/or Roleplay.
Casual Roleplayer: A light mix between being out of character, and in-character. They enjoy their out of character activities, but still enjoy engaging in roleplay on a regular (or somewhat regular) basis. They may or may not participate in deep character development and/or plotting.
Moderate Roleplayer: This player tends to lean more towards their roleplay, than their out of character goals. They enjoy engaging in deep character development, and prefer only a light amount of out-of-character conduct.
Heavy Roleplayer: Full on immersion. This player enjoys staying in character almost 24/7. They may still engage in out-of-character activities, though it is by no means a priority. They enjoy deep character development and plotlines.
Again, any of those are really impossible to nail down. Pretty much any part of those can fit in any of the levels. For example, a roleplayer might enjoy being in-character almost 24/7, and still participate in end-game content. I just don't really see an easy way to nail down anything. Only give a rough example of what different levels most people tend to fall into.
Again, that's just how I see it. Personal opinion.
But if I were to give rough definition of "core" levels?...
Light Roleplayer: A player who may enjoy a form of "No-strings-attached" roleplay. Tends to be out of character more than they are in-character, and generally do not participate in in-depth character development and/or Roleplay.
Casual Roleplayer: A light mix between being out of character, and in-character. They enjoy their out of character activities, but still enjoy engaging in roleplay on a regular (or somewhat regular) basis. They may or may not participate in deep character development and/or plotting.
Moderate Roleplayer: This player tends to lean more towards their roleplay, than their out of character goals. They enjoy engaging in deep character development, and prefer only a light amount of out-of-character conduct.
Heavy Roleplayer: Full on immersion. This player enjoys staying in character almost 24/7. They may still engage in out-of-character activities, though it is by no means a priority. They enjoy deep character development and plotlines.
Again, any of those are really impossible to nail down. Pretty much any part of those can fit in any of the levels. For example, a roleplayer might enjoy being in-character almost 24/7, and still participate in end-game content. I just don't really see an easy way to nail down anything. Only give a rough example of what different levels most people tend to fall into.