这句子有语法错误,
应该是
A la carte means each item is priced and charged seperately.
或
A la carte is a means by which each item is priced and charged seperately.
如你所说
法语 a la carte 就是 with a separate price for each item on the menu ,
句子大致是说
a la carte 是说菜单上每个菜分别计算收钱