I am an american, and I'm new to watching professional soccer. Sometimes I've heard the term 'inverted winger', while paying close attention to context, I cannot make out what it means.
The answer LifeHacks gave is correct but somewhat incomplete. What you are asking is a winger that plays on the "wrong" side judging by the foot preference.
Typically you'd want a left-footed player to play on the left side and a right footed player to be on the right side. Mainly because you would typically use the inside of the foot to cross the ball, as the inside of the foot gives more control on the flight path of the ball. If this does not make sense to you right away, consider the following:
how does the ball path look like when a crossball is "cut" with the inside (here are two nice examples by beckham: ex1 ex2) or outside (here's one such cross and one shot from Queresma) of the foot? In short, the flight path of the ball is towards the goalkeeper if you cross with the outside of your foot (assuming right foot, right wing or left foot left wing).
Can you pass/cross the ball in, with the outside of the boot, whilst running at high pace? The answer is "most likely not" if you are playing on the wing same side as your dominant foot, simply based on the orientation of your body relative to the ball and to the players inside the box to whom you intend to cross the ball.
Both of these observations are valid when a player plays on the "right" wing as their dominant foot. If you for example put a right footed player on the left wing, you could in theory gain the following advantages:
- the player can cross both with the outside and the inside of the foot
- the player can "cut in" and take dangerous shots from around the box as the ball with be on his strong side with the entire 7.35m goal in front of him.
- instead of an trying to cut an early cross, the player can and most likely will want to go deep and dribble in towards the goal (remember where the ball is relative to his body and relative to the goal). This is actually pretty common nowadays; here's one from Arda Turan playing in Atletico Madrid who typically plays as a left winger even though he almost only uses his right foot.
Finally here's an article from the Guardian link explaining the historical aspect of wingers playing on the "wrong" side.
Hope it's more clear now
Posdef has explained in detail what an inverted winger is. However let me get into a bit more detail.
Soccer players no matter how good they are always rated by their goal-scoring ability. So there are a lot of wingers who are amazing goalscorers but will not play as total forwards as being in midfield will allow them to get more of the ball. Ex Messi, Ronaldo, Ribery, Robben. And if you see, all these players will always play as inverted wingers.
Ronaldo perhaps is the Best amongst all of these as he doesnt seem to have a weaker foot but he is not ambidextrous, so his right foot is his stronger foot and hence he tends to play on the left side of midfield so he can cut in and score goals.