I apologize if any of this seems too basic, but I just want to make sure all the bases are covered.
WordPress is software written in PHP. In order to run, it needs a server environment that provides it with a PHP executable and a MySQL database. In order to develop a WordPress site locally, you need the same things. Best practice for local development is to create a virtual machine running an operating system identical to the operating system that your site will be hosted on when you put it on your remote server. Trellis is a collection of scripts that create a virtual machine for this purpose, and configures (on demand) a remote VPS server for deploying your site to. It does this using Ansible (an application written in Python), and Vagrant. Ansible runs the scripts, and Vagrant is used to manage Virtual Machines. This is useful because it isolates your development from your day-to-day operating system, making it easier to catch bugs, do daily work, and avoid having to juggle configuration changes. Whether you use Trellis or not, you will need a local development environment that can fulfill WordPress’s requirements (PHP and MySQL).
“Developing a WordPress site” usually means doing a combination of the following things:
- Coding a WordPress theme (a theme tells WordPress how to display content)
- Creating content with WordPress (i.e. blog posts)
- (optionally) Adding WordPress plugins to add certain functionality (i.e. an event calendar)
- (optionally) Coding WordPress plugins to add certain functionality (i.e. custom post types)
Bedrock provides a system for managing WordPress and WordPress Plugins as dependencies of your overall site. This is useful because it allows you to lock dependencies to specific versions, and track their updates/changes in your repository. It uses Composer to do this, which is a PHP application.
You might also consider talking to the Roots Team about consulting: https://roots.io/services/#consulting They can help you get up to speed and train you on using the Roots stack quickly and easily, and teach you appropriate best practices for WordPress development.