In a true blockchain, only the protocol exists. The protocol is the set of rules that govern how the network operates. There is no central authority that can make decisions about how the network should function. The protocol is what allows the network to be decentralized and distributed.
Other related questions:
Q: Which protocol is used in blockchain?
A: The blockchain protocol is a decentralized protocol that enables secure, trustless and tamper-proof transactions on a distributed ledger.
Q: How many blockchain protocols exist?
A: At the time of writing, there are at least dozens of blockchain protocols in existence, with more likely to be created in the future. Some of the more notable protocols include Bitcoin, Ethereum, Ripple, and Stellar.
Q: What is true blockchain?
A: There is no one answer to this question as blockchain technology is still in its early stages and is constantly evolving. However, one common definition of blockchain is a distributed database that allows for secure, transparent and tamper-proof record-keeping.
Q: What blockchain networks exist?
A: Bitcoin
Ethereum
Ripple
Litecoin
Bitcoin Cash
EOS
Cardano
Stellar
NEO
TRON
Monero
IOTA
Dash
NEM
Ethereum Classic
VeChain
Tezos
Lisk
Zcash
Bytecoin
Decred
Waves
Maker
Dogecoin
Siacoin
Komodo
BitShares
Nxt
DigiByte
Augur
Steem
Ardor
Golem
OmiseGO
Zilliqa
Bitcoin Gold
Basic Attention Token
Factom
IOST
Syscoin
Qtum
Aeternity
Bytom
0x
Icon
Nano
Bitcoin Private
Aion
Pundi X
Populous
Waltonchain
Loopring
DigixDAO
Power Ledger
Ark
MonaCoin
QASH
Dragonchain