AES is the current symmetric encryption standard — 128, 192, or 256-bit key sizes, 128-bit block size. Replaced DES/3DES. Used everywhere: TLS, disk encryption, VPNs, Wi-Fi (WPA2/3).
AES-256 is the gold standard for symmetric encryption. AES is computationally infeasible to brute-force. Security comes from key confidentiality — algorithm is public. Use AES-GCM for authenticated encryption. AES-XTS for disk encryption (BitLocker, FileVault).