1. What is CMS?

CMS or Content Management System is a collection of functions and procedures to properly manage content flow in a collaborative environment. A website CMS, or WCMS for short, according to a definition in Wikipedia word by word "is a software system that provides website authoring, collaboration, and administration tools designed to allow users with little knowledge of web programming languages or markup languages to create and manage website content with relative ease." 

2. What is a Static Website?

A static website is a collection of web pages that are 'fixed' to its current state, displayed as it is by the developer for the website users, as opposed to dynamic websites where the content changes based on the website user's interaction. Read full definition of Static Web Page from Wikipedia here. However, Static Web Page definition is quite loose as a dynamically built website, such as this website, although built to have its content changed over a certain period of time, can be 'static', if there is no user interaction function, or the content of the website has not changed for a long period of time. However, in general web developer terms, Static Web Page are websites created based on HTML and CSS coding and are not database driven. This website, however, was built using Joomla!, a web Content Management System which uses database to store its web pages and allows for easy content management.

3. I hear the term eCommerce and Online Shop very widely used in today's world. Is there any difference between them?

No. eCommerce is a definition to describe electronic commerce where in the basic form, allows the practice of selling and buying products and/or services through electronic medium, commonly the Internet. However, eCommerce is not just about selling and buying online, but the whole trade of any normal retail shop is done online, including marketing, advertising, delivering, and paying for products and services through electronic medium.

An Online Store is loosely to describe a retail store selling products to the consumers over the Internet. The Online Store can showcase its products either a single product or multiple products and/or services in a catalogue, accepts the order online, receive the payment through online communication (even receiving cheques or cash at the end of transaction), and delivering the products or services physically, or through electronic downloads (usually for electronic items such as music, electronic graphics etc.). A website providing buying and selling shares online could also be called an Online Store, as to the base level, eCommerce is about buying and selling online.