@noor_mohammed. Correct. If you are just working offline and exporting csvs to Dropbox/Boxcryptor, you are not connected with any ODK-X server.
If you want to use ODK-X Sync Endpoint instead to manage data, you have to do work setting up the server locally, setting up groups and permissions, and maintaining the server (making sure it stays up, solving any problems) and ensuring sync connections are possible throughout fieldwork. You then have the data all in one spot rather than in separate csvs. The cases in which we found the server particularly helpful were when we had to do things like transfer the data across teams (if one team needed to work on specific cases one week and another needed access to those cases the next week.), or where we needed to add more data during fieldwork or modify data from the central office. That workflow required the bidirectional synchronization that is possible with ODK-X servers. The cases where we did not use a server tended to be where the data just was collected and then submitted (securely) as csvs to the main office. Or when connecting to the server from the field was going to be very difficult (for example, no or very limited internet available).