Applet are the same as Application,
the differece is that they plug in browsers to run (load).
So they connect  to their server  just like the way
stand alone applications do.

So you dont have to refresh your page  to update your
data on applet.

An applet  can be serviced by a server, or can be a graphical plugin
showing an animation like Flash plugins.

If you knew distributed applications or multi tier applications
which their client is a RICH Client (not THIN (not web based client))
you would understand that an applet directly connected to a server
is not a thin client but a rich one.

So there is no need to update it using refeshing your browser,
it can be as powerful as a stand alone application, if it has
enough permission to the client machine's resources.