In this chapter:
(1) "Active employee" means a contributing member of the Teacher Retirement System of Texas who:
(A) is employed by a public school; and
(B) is not entitled to coverage under a plan provided under Chapter 1551 or 1601.
(2) "Carrier" means an insurance company or hospital service corporation authorized by the department under this code or another insurance law of this state to provide any of the insurance coverages, benefits, or services provided by this chapter.
(3) "Fund" means the retired school employees group insurance fund.
(4) "Group program" means the Texas Public School Employees Group Insurance Program authorized by this chapter.
(5) "Health benefit plan" means any group arrangement to provide health care benefits or to pay or reimburse expenses for health care services.
(5-a) "Medicare Advantage plan" means a health benefit plan operated under Part C of the Medicare program.
(5-b) "Medicare prescription drug plan" means a health benefit plan operated under Part D of the Medicare program.
(6) "Public school" means:
(A) a school district;
(B) another educational district whose employees are members of the Teacher Retirement System of Texas;
(C) a regional education service center established under Chapter 8, Education Code; or
(D) an open-enrollment charter school established under Subchapter D, Chapter 12, Education Code.
(7) "Trustee" means the Teacher Retirement System of Texas.
(8) "Usual and customary rate" means the relevant allowable amount as described by the applicable master benefit plan document or policy.