Commands let you modify the attributes of an issue or a set of issues in a single operation. For example, you can assign an issue, change the issue type, raise the priority, link to another issue, add tags, and even post a comment.
Using commands lets you update issues quickly without having to click through multiple menus. They provide a keyboard-centric alternative that reduces the need to constantly switch between keyboard and mouse during data entry. This can save a significant amount of time, especially when dealing with a large number of issues or tasks.
YouTrack keeps track of the commands that you have recently applied to issues, when means if there's a set of changes you use to process issues in a specific way, you can use commands to apply these changes in a consistent manner.