Cryptography is the practice and study of techniques for secure communication in the presence of adversarial behavior.
Some aspects of IT security (specifically confidentiality, integrity, authentication and non-repudiation) are directly related to cryptography.
Cryptographic Algorithms
You can read about encryption (including PKI) on this post.
You can read more about digital certificates on this post.
There is pre-quantum cryptography and post-quantum cryptography.
Pre-quantum cryptography protects against the known attacks without taking into account the theorized arrival of quantum computing.
Post-quantum cryptography adds protection for both existing technology and post-quantum computing.
You can read about pre-quantum cryptographic algorithms on this post.
Cryptographic modes of operation for block ciphers on this post.
You can read about quantum computing, quantum cryptography and post-cryptography on this post.
Cryptographic Attacks
You can find a list of cryptographic attacks on this post.
Cryptography Tools
Cryptography toolkits on this post.
Cryptography tools on this post.
You can find a list of password managers on this post.