I think you already explained it. Checkmate is probably same thing as in regular chess - king is attacked and he can't go anywhere, except that in this type of chess, attacking pieces can't be taken, which means that you can checkmate with queen alone, which is probably still complicated, because your opponent can block the squares with his own pieces. There is probably a lot of possibilities for smothered mate, because knight can't be taken by pawns that are around the king. Imagine that you attack the king with 2 knights... but of course he can put even his queen on the square that you'd like to checkmate him from. There are probably a lot of pins, but no forks, skewers, and other things that just result in capturing a piece. Pieces have little space to move, because opponents pieces block some squares, but on the other hand you can move them on any square that is attacked by opponent's pieces, since you can't hang a piece.
It sounds interesting. After the opening, it is middle-game forever (until someone is checkmated).
I recently witnessed a chess match between two Argentians and am still puzzled as to what type of chess they were playing. The board is setup as normal, and normal moves are made BUT, "no pieces are allowed to be taken" and yet the game ends up in check mate. I'd like to know the type of chess and where do I get those rules....please.