What is rsync?
rsync is a software application for Unix systems which synchronizes files and directories from one location to another and at the same time minimize data transfer using delta encoding when pertinent.

How to transfer data with rsync;

To take back up or transfer data of one or more folder here is the guideline by which you can do it using command rsync. A folder of which you want to take back up is called as source directory and folder where you are taking the backup is called as destination folder.
Let’s assume that you have two folders. First one is backup_source and another is backup_destination.
backup_source is a folder of which you have to take backup into folder backup_destination.
run the simple command to accomplish the task.
rsync -ave backup_source/ backup_destination/
This is simple way from which you can take backup.
Now let us understand the options use in command
1)-a, –archive archive mode; same as -rlptgoD (no -H)
Instead of using several options like -rlptgoD, you can use just a option which is equivalent to the said options.
-r, –recursive recurse into directories
-l, –links copy symlinks as symlinks
-p, –perms preserve permissions
-t, –times preserve times
-g, –group preserve group
-o, –owner preserve owner (super-user only)
-D same as –devices –specials
2)-v, –verbose increase verbosity
3)-e, –rsh=COMMAND specify the remote shell to use

Use the following command especially if you want to take backup from another machine over secure shell.
rsync -ave ssh username@anothermachine/backup_source/ backup_destination