Positions are ranked in order of difficulty, from left to right (the most difficult being on the left):
SS - 2B - CF - 3B - LF/RF - 1B
Moving to the left will reduce Range and Glove; the farther you move to the left, the greater the reduction.
Moving to the right will also reduce Range and Glove, but to a notably lesser amount.
Examples:
There are two major changes to changing player's positions as of the June 2022 update
Note - Position changes to an easier position have always hurt actuals in the short-term, and improved potentials. In the past, that happened at the flip, and the change to actuals was obscured by young players developing at the same time. We did not change how this is calculated, but changing in the middle of the season will now make actuals more clearly go down, before they go back up.
A player can be permanently moved to a different position, with some exceptions:
Once a player's position changes, their actual ratings in Range and Glove will permanently change to reflect the new position they are playing (going down, usually, to some degree based on how difficult the position change is). If moving to a harder position, a player's potential ratings will change in the same fashion, but if moving to an easier position, a player's potential ratings may increase somewhat depending on how much easier the new position is. As a result, there is flexibility in moving a young player from a skill position (such as SS or 2B) to a non-skill position (such as LF/RF), as they will have some time to recover the skills lost.
The effect of multiple permanent position changes over the course of a career can hurt a player's overall fielding skill. Players do better when they get to specialize.
In professional baseball, it is rare to see a player who throws left-handed playing 2B, 3B, SS, or C. As a result, CSFBL will not allow left-handed throwing players to permanently change to these positions. This does not prohibit you from putting a lefty-throwing player in the lineup at one of these positions, but if you do, they will suffer defensive penalties to their Range, Glove, and Arm, with Arm being affected the most and Glove being affected the least.
Non-Catchers can not change positions to Catcher. (You can put non-catchers in the lineup at Catcher, if you so choose, but they'll always be a non-Catcher playing Catcher). Non-Catchers playing Catcher suffer notable penalties to Range (RN) and Glove (GL), and significant penalty to Arm (AR).
Catchers moving to other positions are considered one step to the right of 1B. So, a C moving to other positions is just slightly more difficult than if he was a 1B.