On top it says themes

What does disable pulsing mean?

There are several items that keep pulsing (the rating icons with their golden and silver pulse, some stories which are highlighted for various reasons etc.).

That pulsing can slow down some machines considerably.

So if you choose the option “Disable pulsing” all elements just pulse a single time, after that, they’ll remain in their highlighted form. That should resolve any kind of performance issue you might have.