Filing a patent application is the beginning of the USPTO examination process, not the end.
The USPTO Reviews the Filing
After a U.S. nonprovisional utility application is filed, the USPTO first reviews it for basic filing requirements. Your attorney should receive a Filing Receipt confirming information such as the application number, filing date, inventors, and claimed priority.
Your Application Waits for Examination
The application is then assigned to the appropriate technology area and eventually to a patent examiner. Most utility applications are published about 18 months after their earliest claimed filing date unless a proper nonpublication request applies.
The Examiner Reviews the Claims
The examiner conducts a prior-art search and reviews the patent claims for issues such as patent eligibility, novelty, obviousness, and adequate disclosure. The first substantive communication is commonly an Office Action.
Responding to an Office Action
An Office Action may reject some or all of the claims. That is a normal part of patent prosecution and does not mean the application has failed.
Your patent attorney may respond by explaining why the examiner's position is incorrect, distinguishing the cited prior art, amending the claims, addressing technical or legal issues, or speaking with the examiner.
Allowance, Rejection, and Next Steps
The examiner then reconsiders the application. The process may lead to allowance, additional Office Actions, a final rejection, continued examination, an appeal, or other procedural options.
If the claims are allowed, the USPTO issues a Notice of Allowance. After the required issue fee and remaining requirements are satisfied, the patent can issue.
One important limitation after filing is that new matter generally cannot be added to the original application. Significant improvements developed later may require a separate patent filing.