SHA-3 uses the same Merkle-Damgard iterated construction as MD-5 and SHA-1/SHA-2

SHA-3 supports the same Message Digest sizes as SHA-2, i.e., 224, 256, 384, and 512 bits

SHA-3 is not meant to replace SHA-2 (at least not yet), as SHA-2 is still considered secure.

SHA-3's underlying Keccak function allows for not only ingesting arbitrary length input ("absorbing phase") but also arbitrary length output ("squeezing phase").