Ruby on Rails, often simply referred to as Rails, is a powerful web application framework written in the Ruby programming language. Designed to simplify the development process, Rails follows the Convention over Configuration principle, meaning that it enhances productivity by reducing the need for extensive configuration files. For beginners, gaining a solid understanding of the Rails structure is essential. This includes familiarizing yourself with its key components such as models, views, and controllers (MVC), which work together to create dynamic web applications. Learning these core principles will provide you with a strong foundation to build upon as you delve deeper into web development.

As a beginner, you might find it helpful to explore some fundamental concepts of Ruby on Rails. Here are a few aspects to focus on:

1. Routing: This is the process by which Rails determines which controller and action to invoke based on the URL.
2. Active Record: Rails’ built-in ORM (Object-Relational Mapping) system that simplifies database interactions.
3. Asset Pipeline: A feature that manages JavaScript, CSS, and image files, allowing for efficient organization and optimization.

By understanding these concepts, you will be better equipped to harness the full potential of Ruby on Rails and launch your own web projects with confidence.

As a Ruby developer, leveraging the right gems can significantly enhance your productivity and the performance of your applications. Here’s a look at the top 10 gems every Ruby developer should know:

1. Rails: The foundational framework that powers most web applications.
2. Devise: Simplifies user authentication with a robust set of features.
3. Pry: An advanced alternative to the standard IRB shell, providing helpful debugging tools.
4. Rspec: A powerful tool for test-driven development, allowing you to write clear and expressive tests.

Continuing with our list, here are more essential gems:

6. Sidekiq: Efficient background processing for handling time-consuming tasks.
7. ActiveAdmin: A framework for creating elegant and customizable admin dashboards.
8. FactoryBot: Helps in setting up test data in a clear and maintainable manner.
9. Rubocop: A static code analyzer that helps enforce coding style and quality.
10. Cloudinary: A gem for easy image and video management, enhancing your application’s media capabilities.

Optimizing your Rails application for performance involves a combination of best practices and leveraging the right tools. Start by analyzing the performance of your application using built-in tools like New Relic or Skylight. These tools provide insight into slow database queries and action performance, allowing you to identify the bottlenecks within your application. Additionally, consider implementing caching strategies with Memcached or Redis to store frequently accessed data, reducing load times and improving overall responsiveness.

Another crucial step in optimizing your Rails application is to review and optimize your database queries. Use ActiveRecord efficiently by eager loading associations to avoid the N+1 query problem. Furthermore, consider adding database indexes to columns that are frequently queried, which can significantly speed up read operations. Lastly, ensure your application is running in production mode, as this enables various performance enhancements, including code optimization and asset compilation.