Ecommerce is all about buying and selling online. Whatever you're buying or selling, money is exchanged for goods or services, generally by use of some kind of software bridge from your website to a payment gateway - like PayPal or Stripe.
Ecommerce functionality can be added to your WordPress site through various paid or free plugins - added software (programs) that extend what WordPress can do. Examples include:
For a small business, WordPress with the free version of WooCommerce is more than adequate, provided you have the right hosting environment. This means that WooCommerce works adequately with PHP5, but better with PHP7. In the simplest terms, you’ll need dedicated WordPress hosting from your provider - or the option to upgrade PHP from your cpanel (if you have one).
All that being said, is WordPress good for eCommerce? Sure - WordPress with WooCommerce is certainly good to run an ecommerce site for small businesses with limited budgets. But not a big traffic site like Amazon.
Why the capital letter in the middle? It's an affectation, left over from the early days of programming, when there couldn't be spaces in names. What the programmers did was to run words together with a capital at the beginning of each word so that meaningful - and legible! - names could be given to their programs.