It is an abbreviated form for a variety of meanings, (depending on the context).
I wake up earlier than 6:00 in the morning
I wake up earlier than the birds in the morning
I wake up earlier in the morning during summer, than I do in the winter
I wake up earlier than ever in the morning
On Sundays I wake up earlier in the morning than I do on Mondays when I have to go to work.
PS: Please do not post the same question twice, especially under two different subject headings. See Post:130362