This command will forcefully set the specified player variable to the specified value. The difference between this command and setav is that this command will set the value of the player variable irrespective of all modifiers. For example, if you had +10 sneak from armor and used setav to set your sneak to 20, you'd have a total of 30 sneak but with this command, your total sneak would be 20 as it ignores all factors and changes the absolute value, not the base value.
player.forceav [character variable id] [value]
| Character Variable ID | The ID of the character variable you wish to forcefully change the value of. |
| Value | The value you wish to set the character variable to. |
player.forceav Sneak 3
This command would forcefully set your sneak variable to 3, meaning you would have 3 sneak regardless of all existing boosters/modifiers.