The process of scrambling a message or data as part of cryptography is called encryption. This is what makes the message impossible to read unless you know how to unscramble it using decryption. As the years have gone by this process has become more and more complicated, and there is heavy reliance on computing power and very advanced maths to make it work without risk of the message being compromised.
You may often hear the phrase endpoint when talking about computer equipment. The term refers to devices such as laptop and desktop computers, smartphones and tablet devices ie things which the end user uses to access data.
An extranet is a controlled network environment which is used to give non company staff members access to company resources (for example, data files) typically through some sort of remote access solution.