The Single Supervisory Mechanism (SSM) is one step (of three) in achieving a full European banking union, a key part of the EU Single Market in financial services. The others are the Deposit Guarantee Scheme (DGS) and the proposal on Banking Resolution and Recovery (BRR).
Full version PDF of the PIIGSty YEUr Tidbit Factsheet here: YEUr PIIGSty Tidbit: SSM