So there are two kinds of VPNS, we call itis intranet when it is built to connect the branches in a company, and we callit an extranet when it is built for a company to connect to its partners and customers.

Imagine your LAN is a island, if you want to connect to other island, the usual ways to go there is to take a ferry, but taking ferry means you will have no privacy, whatever you do is to be seen someone else.

And the other way is to build a bridge between two islands, it is secure and fast. But it is extremely expensive to build and maintain.

So VPN is like a submarine, the perfect way with security and reliability when connecting two islands, and the cost is affordable.

Susceptible: easy to be influenced by other people or things.

Span: a period length of time.

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to summarize, blockchain

is a data structure.

A decentralized operating system, each nodeshould be equal and has no higher authority over another.

The transactions on it is immutable andtotally transparent, append only.

Many incentivize owners in the forms of tokens which can be used across the internet, and in return, they keep the blockchain safe.

Blockchain is not one item, thing or afeature.

It is all at once, some of them workingtogether while others independently.

When 1995, people considered “Web” as having 5 identities, each one can be taken advantage of by developing different strategy. But no one had predicted the hotness of social network such as Facebook.

Blockchain has ten properties below:

Digital currency

Computing infrastructure

Financial service markets

Trust layer service

Decentralized ledger

Peer-to-peer network

Transactions platform

Open source software

Append: to attach to at the end of something.