Using a local machine or a secure network connection, the rsync command synchronizes files from a source to a destination. It serves as a quick, adaptable, and secure alternative to the rcp command. 

A quick and incredibly versatile tool for copying files is rsync. It can copy to or from a remote rsync daemon, another host over any remote shell, or locally. It provides a vast array of controls that allow for very flexible specifications of the list of files to be copied as well as complete control over every aspect of its behavior. It is well-known for its delta-transfer method, which minimizes the amount of data transmitted over the network by only transferring the differences between the source files and the already-existing files at the destination. rsync is frequently used as a better copy command for everyday use, mirroring, and backups.

By default, the "quick check" technique used by rsync looks for files that have changed in size or last-modified time to identify those that need to be transferred. When the fast check shows that the file's data does not require updating, any modifications to the other preserved attributes (as requested by options) are made immediately on the destination file.

rsync has a few more features, including 

1. Copying links, devices, owners, groups, and permissions supported.

2. Like GNU tar, exclude and exclude-from options

3. Use any transparent remote shell, such as ssh or rsh, to ignore the same files that CVS would ignore with a CVS exclude mode.

4. does not call for super-user rights

5. File transfers are pipelined to reduce latency expenses.

6. support for rsync daemons that are anonymous or authenticated (ideal for mirroring)

Syntax:

Local use:

Access via a remote shell (PULL):  

Access via a remote shell (PUSH):