Backup \ file synchronization via USB drive?

Question

Data synchronization

Please, tell me a simple program for backup \ synchronization in the background.
The bottom line is this:
- I work with the files of a certain directory on PC1 with the program installed
- When you connect an HDD, with a certain identifier (validated), the files are synchronized (replaced in both directions by change time or weight, created, deleted).
- I connect the HDD to PC2 with the installed program, I get the same file structure in the specified directory as on PC1.
Searching gives many solutions, but trying everything will take a lot of time. Interested in your opinion, what do you recommend?

Answer 1

and they are not
simple
, everything with bells and whistles,
you can start with this one, or you can immediately go to Acronis one
more