这两者指的都是市场锁定。在公司进行IPO时，承销商（underwriter）往往会需要企业要求其现有股东在IPO后一段时间内不得出售其持有的股份。这一约束性条款的目的就在于禁止对当前存在的证券进行交易，直至在IPO过后市场可以吸纳额外的股份出售。In connection with the initial public offering of a company, the underwriters will generally require the company to prevent their existing stockholders from selling their shares for a certain period after the offering (with 180 days being standard). The purpose of this “market standoff” or “lock up” is to delay the trading of these existing securities until the market can absorb the additional sales after the IPO. To avoid potential disagreements with shareholders immediately prior to the offering, the lock-up provision is typically contained in agreements in connection with every issuance of company stock.

美股中的这一规定与我国新股上市后原股东的限售期规定起到相同作用。标准的standoff或lockup期间为180天。

该条款通常会在股权投资协议中出现，但在企业IPO时，股票承销商为了避免承销股票遭受损失，也会要求企业签订该条款。

以下为某协议中的双语条款，供参考：

All of the Company’s issued and outstanding Ordinary Shares and all the Company’s underlying outstanding options are subject to (i) a right of first refusal in favor of the Company upon any proposed transfer (other than transfers for estate planning purposes); and (ii) a lock-up or market standoff agreement of not less than 180 days following the Company’s initial public offering pursuant to a registration statement filed with the SEC under the Securities Act.

公司的全部已发行并流通的普通股份以及公司的全部优先流通期权均受限于：(i)在任何拟议转让（不包括为产业规划目的之转让）时，有利于公司的优先购买权；以及 (ii)公司按照在《证券法》下向SEC备案的登记声明，首次公开发行后，不少于180天的市场锁定约定。