A standard license is activated and linked to one computer at a time. Let's say you have a 100VU standard license, then you can run your tests from one controller up to 100 concurrent virtual users.

Now let's say that you have a 100 VU shared license instead. That license is activated on the NTS server (license server) and linked to it.

Then you could have two different controller's that will lease and use 50 VU each to run your tests in parallel against  same or different applications.

For more information you can check the Neotys web site here