What Distiguishes Different Classes of Player?

Hi all.

This is my first blog post. Writing just out of curiosity. I have been playing chess for the past 30 years. I rate myself as an average player but slightly underrated since I am not actively participating in FIDE-rated tournaments and never experienced structured chess learning back then.
However, since 2020 (during the pandemic), I have taken chess seriously. I self-studied chess, watched videos, played online tournaments, and asked a lot of questions about chess from various master-level players. I believe one of the many questions amateurs like me always wonder is what makes someone better in chess than the other.

One of my friends (He is an expert-level player with FIDE 2150) summed it up nicely. He said, there are 3 elements that distinguish one player from the others which are:

1. Knowledge
2. Understanding
3. Concentration

Knowledge
Knowledge is about knowing about chess rules, principles, basic tactical motifs, mating patterns, opening theory, middlegame concept, endgame theory, and everything. Acquiring chess knowledge is the first thing we need to become a chess player. The knowledge gap between beginners (let's say 0-1000 rating) and advanced players (1500-1900) are huge compared to the knowledge gap between advanced player and expert level (2000-2200).

Understanding
A knowledgeable player who can quote every chess concept. principles and theories do not necessarily have an in-depth understanding of what he just quoted. For example, most chess players, even a beginner can memorize opening principles. Let's say, "Activate Your Pieces" or "King Safety", but still have no clue of what those principles really meant. Understanding is one of the key distinguishers between a weak and a strong player. That is why a super GM can easily outplay an IM or lower-rated GM despite playing obscure opening lines. The player who has a greater understanding knows how to prioritize conflicting chess principles and when to apply them accurately.

Concentration
Concentration is the final element that makes a great player great. Missed wins and blunders are most likely due to a lack of concentration. For advanced to master-level players, especially when two players have similar levels of rating, concentration is often the tie-breaker. Sometimes, even a lower-rated player managed to win against a much higher-rated opponent due to a lack of concentration. Concentration is likely influenced by other factors like stamina, emotional state, and determination.

Do you agree? Appreciate it if you guys can share your feedback, especially those who are titled players.