請問關於offer letter內容裡面的"At-will" employment - offer

小弟最近拿到一家公司的offer letter
因為是第一次找工作,所以沒有任何經驗
請問offer letter內容需要注意些什麼?
offer letter有一段關於"At-will" employment

原文如下

"At-will" employment

Your employment with xxxx(company name) will be "at-will".
Either you or xxxx may terminate your employment at any time for any reason,
with or without cause or notice.
xxxx may make other employment decisions and may change any of the terms and
conditions of your employment, including the terms and conditions set forth
in this letter, at any time for any reason, with or without cause or notice.
This "at will" relationship may be changed only by an express written
agreement, signed by both you and the present of xxxx.

懇請各位大大解釋一下是否公司的offer letter都會有這一段??

非常感謝各位的幫忙^^

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