A cascading restraint states the same restriction several times over, from broadest to narrowest, so that if a court strikes down the widest version, the next narrowest one still stands.
Technically, it is a drafting technique expressing a single restraint as multiple alternative formulations of decreasing scope, varying the period, geographic area, and prohibited activity, relying on the blue pencil doctrine (and the more permissive read-down power under the Restraints of Trade Act 1976 (NSW)) to let a court fall back to a narrower formulation if the broadest one fails.
Buyers favour cascading restraints because they cost nothing to include and can only help the buyer if challenged: the worst case is the court falls back to the narrowest tier, which is still a real restraint. For the seller, a cascading restraint means the headline, broadest version is the one you should assume will actually be relied upon and negotiated against, not the fallback positions.
Cascading restraints are standard practice in Australian sale-of-business agreements and are treated differently from employment restraints, where recent reform proposals have specifically targeted the technique.
What you as a seller should push back on: treating the narrowest tier of a cascading restraint as the real one during negotiation. Negotiate the broadest tier as though it is the operative restraint, because that is the version you are actually agreeing to.