What is Composer?
Composer is a dependency manager. The introduction to Composer from the official website sums this up quite nicely:
It is definitely worth having a read through the official Composer documentation, which is clear and comprehensive.
Introduction – Composer
https://getcomposer.org/doc/00-intro.md
What are dependencies?
So, we know that Composer is for dependency management, but what are dependencies? Well, simply put, they are modules of code that your main application depends on. Those modules can be third party, or they can be your own first-party modules that you share between your applications.
Let's say that your application needs to send emails. You could roll your own email sending system in pure PHP and use the mail function for this.
PHP: mail –...