Firm offer 是：实盘、肯定报价 的意思
counter offer 是：还盘、还价 的意思,例如,你提出成交价为5元每斤,对方提出4元一斤,此处的4元一斤为还价及counter offer.如果你接受了对方提出的还价,这个还价便成为 an accepted counter offer.
以下是一些有关offer的解释：
offer 报盘,报价
to offer for 对……报价
to make an offer for 对……报盘（报价）
firm offer 实盘
non-firm offer 虚盘
to forward an offer (or to send an offer) 寄送报盘
to get an offer(or to obtain an offer) 获得……报盘
to cable an offer (or to telegraph an offer) 电报（进行）报价
offer and acceptance by post 通过邮政报价及接受
to accept an offer 接受报盘
to entertain an offer 考虑报盘
to give an offer 给...报盘
to submit an offer 提交报盘
official offer 正式报价（报盘）
回答补充：an accepted counter offer 是对方提出了还价后才接受的报价.a firm offer 是指最初提出的报价,还没经过对方的还价,也没有被对方接受.
