Anti-Seize Pastes provide a protective barrier that stops prevents galvanic corrosion and eventual seizing of metal to metal interfaces, such as threads or cassette splines.
While many people just use grease on threads, grease often isn't the best choice. Grease is typically designed for lubrication of moving parts, and 90% of the time you don't want bolts moving once you've torqued them to spec. That's where anti-seize pastes come in - they prevent seizing without encouraging movement (loosening).
Other places we highly recommend using Anti Seize include centerlock rotor and cassette splines, along with threaded, thread-together and certain press-fit bottom brackets*.
*Anti-seize is only applicable in certain scenarios involving press-fit bottom brackets - please get in touch if you have any questions.