1)
What is the difference between "Tefilah" and "Tachanunosai"?
1.
Malbim: Tefilah is pouring the Nefesh and clinging to its source. Techinah and other expressions of prayer refer to requesting needs. Tefilah is elevation of the Nefesh from all physical matters. When Hashem hearkens to Tefilah, He also heeds requests of the body for its needs.
2)
Why does it say "Tachanunosai"?
1.
Radak: I make many supplications to You at the time of my affliction.
