Trying to understand TID definition from PostgreSQL documentation
&ldquo;Page&rdquo; and &ldquo;block&rdquo; are synonyms in PostgreSQL and refer to the 8KB block of data that is the unit for all object storage. One tends to use the term &ldquo;block&rdquo; when speaking of disk storage and &ldquo;page&rdquo; when the data reside in memory, but it is the same.

So a tid of (42,9) means that the item is the ninth element in the 43rd 8KB block of the table or index (blocks are counted from 0).