In the classic setup your entire structure lives inside one binary file. In project mode that same structure sits on disk as a folder of readable files: methods, forms and settings each separate. Technically a small shift. In practice, what changes most is how you collaborate.

What you gain

• Version control that actually works. With Git you can see who changed which line, and when. With a binary file you could only keep whole copies and hope the date in the filename was right.
• Readable differences. You can put two versions side by side and see exactly what changed — when reviewing work, or when asking when something broke.
• Working with more than one person. Two developers can work on different parts and merge the result.
• Automation. Building and testing can be done by a script instead of by hand.

What changes in daily work

Less than you would expect. You still work in the same environment, with the same editors. The difference is in what happens on disk, and in what that makes possible.

What does change is the discipline. A folder of files needs agreements: who puts what where, when things get merged, and what does not belong in version control at all.

What to watch for

• The conversion itself is usually the smallest part of the work. Setting up version control and the conventions around it takes longer than the conversion does.
• Not everything belongs in version control. Data, log files and local settings stay outside.
• If you work alone today the gain is smaller. But the day somebody else has to work on the code, the difference is large — and that includes you, two years from now.

If you want to combine the move to project mode with cleaning up and documenting the code, that falls under code assistance.