These three terms sound similar but do different jobs. Here's how to tell them apart.
Sort type — how products are ranked
A sort type is a single rule that ranks every product in a collection, such as Best Selling, Revenue, Newest, Price, or Most Viewed. It answers the question "in what order should these products appear?" This is the building block everything else uses. See Sort Types.
Segment — which products are grouped together
Multi-segment sorting lets you split one collection into ordered groups, each with its own rule, and each group can have its own sort type. For example: show new arrivals first (sorted newest-first), then full-price best sellers, then everything else. Products that don't match any segment fall into a default group at the end, ranked by the collection's main sort type. Use segments when one ranking rule isn't enough for the whole collection. See Create Multi-Segment Sorting.
Strategy — a saved set of settings you reuse
A merchandising strategy bundles a sort configuration (sort type, push-down rules, segments and so on) into a named template you can apply to many collections at once — and even set as the default for new collections. Use a strategy when you want consistent merchandising across lots of collections without configuring each one by hand. See Merchandising strategy.
In short
Sort type = the ranking rule.
Segment = sections within a collection, each with its own ranking rule.
Strategy = a reusable bundle of settings applied across collections.