Rugby League is different to the Rugby that is played in North America more commonly at colleges etc. It's similar enough for those who know of Rugby Union to not need an explanation but for those who aren't I'll try my best to give you an explanation.
The game as best I can describe:
Spoiler: show
The on field positions are as follows:
1 - Fullback - The player is often the most athletic and fit player in an NRL team and more recently also acts as a secondary playmaker (Quarterback) on offense. They are called on to finish set plays for tries (touchdowns), and are often also required to pass and kick the ball though not as frequently as the five-eighth or halfback. In defense they stand behind the line and act as the last line of defense when someone breaks the line, and communicate to the defensive line (other 12 players) to ensure the defensive line is sound and there are no glaring gaps for the attacking team to run through. They also field kicks and subsequently are the most common producer of kick returns. Some great fullbacks include Billy Slater, James Tedesco and Jarryd Hayne.
2 and 5 - Winger - These players play on the edge of the field on both sides. They aren't usually required to be skilled passers or kickers but are generally fast and often also large. They are also generally athletic and the best of them create some excellent highlights by catching kicks for tries or contorting their bodies to get the ball on the ground over the line. In defense they are the least important player though they also field kicks that are kicked to the edge of the field and also are important kick returners. Wingers these days are also expected to act as forwards during the early tackles of a set as they are already back when the kick is made, while the forwards are still retreating to get behind the play and do their "hit ups". In the modern era some of the best wingers include Josh Mansour, Jordan Rapana and Blake Ferguson.
3 and 4 - Centre - These players stand one in from the winger. They are called centres because they are the centre of backline plays traditionally though it's probably not the best name for them these days (old hat). They are generally required to be the most versatile players, fast, strong and they are important defenders as this section of the field is the most attacked by the opposing skilled players. Some centres also possess good short attacking kicking games. They are often the last to pass to a winger when the attacking motion causes an overlap so they need to be deft passers of the ball too. Some great centres include Mark Gasnier, Steve Renouf and Jamie Lyon.
6 - Five eighth - These players are a second playmaker who often will act as more of a running playmaker to the halfbacks passing/kicking playmaker, though the best five-eights can do all three well. They usually receive the ball second from the play the ball during backline movements though some teams favour having left and right sided halves that both act as first receivers. Some of the greatest players of all time are five-eighths (Wally Lewis, Darren Lockyer, Brad Fittler). In defence they will usually defend on the inside of the centre on one side of the field, with the halfback on the other side.
7 - Halfback - These players are the primary playmaker and the most similar to a QB. They act as the first receiver during set plays and call most of the plays on the field. They are generally the primary field position kicker and the most likely to be goal kickers. Some all time great halfbacks include Andrew Johns, Jonathan Thurston (though he played 7 and 6), Ricky Stuart, Allan Langer and Peter Sterling.
8 and 10 - Prop - These are generally the largest, strongest and meanest players on the field. Their role is to run through the centre of the field into the opposition props to try to gain field position (and of course the opposite).
9 - Hooker - Hookers are usually the person in charge of picking the ball up on the play the ball and issuing the first pass. As such they are in many ways even more important of a playmaker than the halves, though less flashy, usually being relied on to send the ball to the right person at the right time. Great hookers also possess great kicking games. Cameron Smith is considered the best currently playing and has a case for being the best ever.
11 an 12 - Second Row - Second rowers are arguably the most athletic players on the field. They need to be big AND strong and are most like tight ends and linebackers. They are required to make loads of tackles and are usually the best at it. Great second rowers will also be great try scorers (Steve Menzies). They defend on the inside of one of the 6 or 7 next to the prop.
13 - Lock - This is a versatile position that can change depending on the game plan of the team. These days most locks are fitter props who are interchanged less but generally play the same role. Sometimes they play more like a larger, more strong half and some good locks can also kick though this is rare these days. Jason Taumalolo is the best lock in the world.
The Teams
There is a great Reddit post that should help you choose a team.
I support the Wests Tigers. They are ... the suck. If you want to get in on the ground floor by all means help me root for the losingest team in the NRL.
The current premiers are the Sydney Roosters who just buy the best players and hoard them.
Anyway now that I have gone to this effort you are all obliged to pick a team and follow the NRL this season. Thx.