Path your files are stored on host machine, more information.

Windows users: You must use forward-slash c:/dev/vagrant/webroot or double back-slash c:\\dev\\vagrant\\webroot

Path your hosts' files are mounted on guest machine, more information.
This is the slowest option of all. More information.
NFS is highly recommended for OSX and Linux! Make sure to install the
Windows only, and highly recommended. More information.
If you are on Windows you need rsync installed. The simplest way
The host IP where the SMB mount is located. If this isn't specified, Vagrant will attempt to determine this automatically.
The username used for authentication to mount the SMB mount. This is the username to access the mount, not the username of the account where the folder is being mounted to. This is usually your Windows username. If this isn't specified, Vagrant will prompt you for it.
The password used for authentication to mount the SMB mount. This is the password for the username specified by smb_username. If this is not specified, Vagrant will prompt you for it. It is highly recommended that you do not set this, since it would expose your password directly in your config.yaml.
A list of arguments to supply to rsync.
Files or directories to exclude from the sync.
Vagrant's rsync-auto will watch and automatically sync this folder.
Vagrant's rsync-auto will not watch and automatically sync this folder.