The lowest level of the index is the leaf level. At the leaf level, the index contains a key value for each row in the table, and the rows are stored in sorted order by the index key:
For clustered indexes on allpages-locked tables, the leaf level is the data. No other level of the index contains one index row for each data row.
For nonclustered indexes and clustered indexes on data-only-locked tables, the leaf level contains the index key value for each row, a pointer to the page where the row is stored, and a pointer to the rows on the data page.
The leaf level is the level just above the data; it contains one index row for each data row. Index rows on the index page are stored in key value order.