What units are 'reads' and 'writes' in dm_exec_query_stats

Question

MSDN describes the various logical / physical read and write columns in dm_exec_query_stats as:

Number of physical reads performed the last time the plan was executed.

Those columns are all 64 bit ints (bigint), so obviously larger numbers represent more reads / writes.

But what are the units of this column? Database pages? Kilobytes? Just an arbitrary number?

Example: for a reasonably expensive query in my database dm_exec_query_stats.total_logical_reads = 40412.

40412 of what?