Read about patches and the PatchTool here: Patches and Service Pack
A tip for anyone using the PatchTool for Acumatica 25R1+ patches that might not be obvious: When you download the latest PatchTool.zip file, it could be tagged as "blocked" by Windows because it came from another computer. If you just use Windows to extract it, all of the extracted files will also be blocked. As a result, when running the PatchTool, it may not use the correct .dll version needed and throw an error due to incompatibility of binaries. To avoid this issue, options are:
After downloading, unblock the .zip file through the file properties dialog checkbox before extracting files,
Unblock the contents of the .zip file after extracting the files
Use a 3rd party compression tool like 7zip to extract the files.,
Modify Windows group policy to unblock files from the download folder. (not really recommended due to security risks)