RNG Random Number Generator
Generates (pseudo-)random numbers. Two classes: PRNG (deterministic from seed, for games/simulation) and CSPRNG (cryptographically secure, for keys/tokens).
Classic PRNGs: Mersenne Twister (1997), xorshift, PCG. CSPRNGs: ChaCha20-based in Linux /dev/urandom, getrandom() syscall. Never use rand() for crypto — always getrandom/crypto.getRandomValues. Game RNG controversies in the 2010s: lootboxes, "rigged" feeling (often it's correct randomness that looks weird). Modern hardware RNG: Intel RDRAND, ARM TRNG (but often controversial regarding backdoor concerns).