Namespace
Namespace on EOS is similar to the letters at the end of URLs (e.g. .com or .net). Users on EOS can win their suffixes on namespace auctions and add the suffix at the end of the account name.
Network
On EOS this term means one of the resources available for users. The term 'Network' is used for the throughput capacity of the blockchain. Staking tokens for Network allows using the respective portion of the blockchain capacity.
Node
Any device or server connected to the EOS blockchain with the nodeos software on.
Open Source
The EOS Constitution proclaims that all the EOS smart contracts must be open source so the source code can be reviewed, copied or modified by anyone.
Oracle
A system transitioning the off-chain data to the blockchain. The data arranged as smart contracts forms a body of diverse statistics that can be used for different purposes.
Owner Permission
In the account permissions hierarchy, the owner permission is the top authority. This permission can be used for signing for any possible case where the lower-level permission is required. Alongside the active permission, the Owner Permission is associated with the new account by default.
Permissions
EOSIO is the first blockchain operating with the account structure. On EOSIO users can delegate permissions to execute different actions available for the account.
Proof of Work
Proof of Work (PoW) is a consensus mechanism. First, it was used by the Bitcoin blockchain. Now, this mechanism is used by many other blockchains. On PoW blockchains, users have to solve the math problems using their devices in order to find the proper hash for the next block. The difficulty of these task grows with the time and secures the blockchain from 51% attack keeping it decentralized.
Private Key
A private key is a string of symbols used for authentication of the owner of the account so nobody else can perform actions. Each private key is associated with a particular public key.
Proxy
When a user calls the 'regproxy' action, she/he registers as a proxy — a user that can utilize the voting weight delegated by others. Moreover, the very procedure of delegating of voting power can be called "proxy" (the user A proxies her/his voting power to the user B).
Public Key
A public key is the part of the pair of keys (public and private keys) available for the public. The public key can be shared publicly without compromising user data or assets.
RAM
RAM means Random Access Memory. On EOS RAM is one of the most valuable resources and it is used for the search of the data stored on EOS. On EOS users have to buy RAM, not stake coins to get some.
Refund
On EOS refund (after unstaking tokens) takes 72 hours.
Registration
In the times of transition of EOS token to the platform separate from Ethereum, the users were asked to register their tokens via mapping tokens to public keys.
Resources
There are three basic resources circulating on EOS: RAM, Network, and CPU. RAM is a persistent resource (it's bought and used privately until the total fade). CPU and Network are transient resources (it means that after the use these resources regenerate).
REX - Resource Exchange
On EOS CPU Bandwidth and Network Bandwidth can be delegated to others. It is possible to rent out the resources to others. REX is a smart contract written by Block.one that serves as a decentralized resource exchange. REX contains the pool based on a Bancor relay which distributes the collected interest between the lenders on the platform. REX is available only for those who vote for at least 21 Block Producers (personally or via proxy).
Ricardian Contract
The Constitution proclaims that each smart contract (written in a scripting language) should be accompanied by a human-readable version of this contract. Such a version is called the Ricardian Contract.