...can block plugins which you enable once via click-to-play or permanently by white-listing domains that they load content from.
Java Applets, Flash movies/applications, Quicktime clips, PDF documents and other content won't be even downloaded from sites where you consider them annoyances or dangers, saving your bandwidth and increasing your navigation speed.
NoScript's settings for blocking plug-ins can be found in:
NoScript Preferences → Embedded Content
However, because it's so powerful and configurable, it can be difficult to use for newcomers and takes a while to setup.