Page vs Slice when to use which?

Page extends Slice and knows the total number of elements and pages available by triggering a count query. From the Spring Data JPA documentation:

A Page knows about the total number of elements and pages available. It does so by the infrastructure triggering a count query to calculate the overall number. As this might be expensive depending on the store used, Slice can be used as return instead. A Slice only knows about whether there’s a next Slice available which might be just sufficient when walking through a larger result set.