rsync command is used to sync two devices but in that I have to give the command each time when I switch on my PC and then it starts to work. Does rsync daemon helps to synchronize two devices automatically and continuously? Like whenever I switch on my PC, rsync command run automatically and update files between two devices.
rsync is for synchronising files between two PC on demand (and only then).
rsyncd, i.e. the daemon allows setting up a PC as a file server and allows finely graining access rights, i.e. who (or which user group) may access which files with which file permissions.
If you want this to be done regularly, you'll have to set up a(n) (
cronjob or, for one-time synchronisation upon booting, a boot script would work,too.
rsync in daemon mode just gives you a way to send/receive data to the server without using other protocols such as ssh. It can be useful for speeding up the data transfer for example, or when ssh or other protocols are not available. Also look on "unison", it seems to me that it can be useful in your case.