PKCS #11 is one of the Public-Key Cryptography Standards and also refers to the programming interface to create and manipulate cryptographic tokens. It is a platform-independent API developed by the global non-rofit organization named OASIS. The API defines commonly used cryptographic object types (RSA keys, X.509 Certificates, DES/Triple DES keys, etc.) and all the functions needed to use, create/generate, modify and delete those objects. PKCS #11 is used in devices like hardware security modules and smart cards.
OASIS stands for Organization for the Advancement of Structured Information Standards and is a nonprofit consortium that drives the development, convergence and adoption of open standards for the global information society. You can read more about PKCS #11 and OASIS here