How to understand Frenopolis in the context of Chess:
A chess board is composed of 2 colors (black and white) and 6 unique pieces (king, queen, rook, bishop, knight, and pawn).

The identity of each piece is characterized by its unique movement on the board. For example:
Pawn: Moves 1 square forward
Knight: Moves 2 then 1 perpendicular
Bishop: Moves diagonally on its color.
Rook: Moves horizontally.
King: Moves in 1 in any direction.
Queen: Moves diagonally or horizontally.

If you were to assign each of these movements an identifier (abstract them), you would end up with something like this:
Pawn: Move 1 square forward = P
Knight: Move 2 then 1 perpendicular = N
Bishop: Move diagonally on its color. = B
Rook: Move horizontally. = R
King: Move 1 in any direction. = K
Queen: Move diagonally or horizontally. = Q

In this way, you could define the Queen's movement (moves diagonally or horizontally) as:
>Queen = Moves horizontally (Rook “R”) + Moves diagonally on its color (Bishop “B”)
>Queen = Rook + Bishop
Queen = R + B

If you understand how a Chess piece's movement can be abstracted from the piece, you can understand how Frenopolis is constructed.