What is a Trademark Office Action
An office action is an official letter sent by the USPTO. In it, an examining attorney lists any legal problems with your chosen trademark, as well as with the application itself. You must resolve all legal problems in the office action before we can register your trademark.
In an office action, an examining attorney may require that you fix legal problems with the application itself (“requirements”) by making simple revisions, such as clarifying your goods or services. An examining attorney may also raise legal rejections (“refusals”), such as refusing your application because your chosen trademark is likely to be confused with an already registered trademark. However, you may not always be able to fix a requirement or a refusal. See the section on this page called ”Responding to common refusals or requirements.”
Some office actions require a written response to fix major legal problems, others suggest calling or emailing the examining attorney to fix minor legal problems, and others may require no response at all. Read your office action carefully to determine how and whether you need to respond.
Source: USPTO.GOV