Tier 1 Capital vs. Tier 2 Capital: What's the Difference?
https://www.investopedia.com/ask/answers/043015/what-difference-between-tier-1-capital-and-tier-2-capital.asp
Tier 1 capital and tier 2 capital refer to different bank holdings, as defined by the Basel Accord. The capital adequacy ratio (CAR) defines the amount of both tier 1, core capital, and tier 2, supplemental capital, a bank must hold.