The MD Link monitor's function is to communicate with the MD Link service. Since the MD Link service has no GUI, it needs a separate program in order for the user to administrate it - and the MD Link monitor is just that.
The first and most obvious function of the monitor is to display information about what is happening within the service. From here, the monitor can also send certain commands to the service, to influence what is happening within it.
The monitor communicates with the service over TCP/IP, so the monitor and service can be on different machines, as long as these machines can reach each other and are unimpeded by firewalls etc. By default the service listens on TCP port 9500.
To be precise, the monitor can be set up to communicate with any number of services. For simplicity, and since most MD Link installations will only need one service, the following documentation will often refer to 'the service' when this in fact means 'any service that the MD Link monitor is pointed at.'
Start the monitor by selecting it from MD Link's start menu on Windows, or by running the 'monitor' executable on Unix.
Every text window in the Studio (and Monitor) has some standard keyboard shortcuts available. Press ctrl-f to bring up a Find dialog, ctrl-h for Find & Replace, and ctrl-g for Go To Line. Also, in editable text windows you can select multiple lines (with shift+arrows, or the mouse) and then press tab or shift-tab to do a multi-line indent or un-indent.