It forms a partition between the nasal passages and the mouth. This partition is continued deeper into the mouth by a fleshy extension called the soft palate.
The interaction between the tongue and the hard palate is essential in the formation of certain speech sounds, notably. Also surrounds the teeth to protect them.
Cleft
In the birth defect called cleft palate, the left and right portions of this plate are not joined, forming a gap between the mouth and nasal passage (a related defect affecting the face is cleft lip).
Cleft palate has a severe impact upon the ability to nurse and speak but is now cured through reconstructive surgical procedures at an early age (where such procedures are available).