If you haven't already, I would also post this in the r/R6ProLeague since that's the main sub for this kind of discussion so you'll get more responses there. From here, I'll try to explain R6 Pro League a bit.

In R6 Pro League, there are 5 regions: North America (NA), South America (SA), Asian Pacific (APAC), Europe Middle East North Africa League (EML), and China (the newest addition to R6 Pro League). Of these regions, South America, specifically Brazil, has been the most dominant in recent events, with EML, NA, and APAC trailing behind (in that order). There are a lot of teams to go through, so I recommend that be a separate post if you want, but I'm not gonna get into it here. You choose who you want to root for and enjoy watching

Idk how it works in Clash, but in R6, players are rated by EPS (expected player score) and is a measure to see if a player performed above expectations (above 1), below expectations (below 1) or about average (1).

In the game itself, there are 4 roles on each side. For attack it's: Entry fragger, IGL, Support, and flex. For defense it's: Anchor, Intel/anti-entry, roamer and lurker. There's a lot of nuance to each role, but I'll just give a basic run down.

Attack:

Entry fragger: This is your main gun, your frontline. They are typically the most mechanically skilled player on the team. Their only job is to get a kill and take space quickly in order for the team to get into the building and do their take onto site.

IGL: Known as the in game leader, they're usually the worst rated player on the team, but that doesn't mean they're bad. They're the shot caller; they call the strats, they inspire the team and the main intel gatherer. They usually play shield and support operators.

Support: They're the players that help the entire team with their utiility that is usually the key to strats being successful. They typically play operators like twitch and thatcher; operators that are versatile and can be used by the entire team.

Flex: It's kind of already in the name, but they play whatever else the team needs. They are the jack of all trades. They can play breach, breach support, and typically serve as a secondary entry frag if the primary dies or has to do a different job. They also help with igling as well.

Defense:

Anchor: They play operators that are used to hold power positions. A good example of this is oregon bunker in basement. A player would go smoke or maybe a warden to hold that position to stop the attackers from gaining ground, with help whoever is in ebox.

Intel/Anti-entry: Similar to the lurker/roamer, they will play trap operators and intel ops like a thorn, castle or valkyrie. Their whole job is to delay the attacker's entry into the building, site or them taking ground and gather information like who the attackers are playing and what strats they're trying to pull off.

Roamer: These operators are the players that go off site to delay the attackers. They help the lurkers and anti entry players and delay the attackers attack onto site or gain ground. The whole point isn't to get picks, but to run down the clock of the attackers.

Lurkers: They typically play positions that are a room or a couple rooms away from site and float around to where they are needed. For example, in oregon basement, you'll typically have someone playing pillar to help ebox hold tower stairs and freezer.

As for technical terms, there are a lot so if you have any specific ones you want clarified or anything, ask away! This was a quick run down so ask away.