Ruby on Rails, often simply referred to as Rails, is an open-source web application framework written in the Ruby programming language. It is designed to make programming web applications easier by making assumptions about what every developer needs to get started. This framework follows the Convention over Configuration principle, which means that developers aren’t required to specify every little detail of their application but can instead adhere to established conventions. Furthermore, Rails promotes the use of DRY (Don't Repeat Yourself) principle, fostering cleaner, more maintainable code.

For beginners, diving into the world of Ruby on Rails can be both exciting and daunting. To get started, you'll need to install Ruby and Rails on your machine. A great resource for installation is the official Rails installation guide. Once you have everything set up, you can begin creating a simple application using the command line. Rails provides a powerful set of tools that streamline the development process, from generating application structure to deploying your app. Familiarizing yourself with the Rails community and exploring available resources will greatly enhance your learning experience and keep you updated on best practices within the framework.

As a Ruby developer, mastering the right tools is essential to improve productivity and enhance code quality. Here are the Top 10 Gems that every Ruby developer should know:

1. Rails - The most popular web application framework, it allows developers to create high-quality web applications quickly and efficiently.
2. RSpec - A behavior-driven development (BDD) framework, RSpec is crucial for writing tests and ensuring code reliability.
3. Devise - An authentication solution for Rails applications that provides a robust set of functionalities for user management.
4. Factory Bot - A library for setting up Ruby objects as test data, simplifying the creation of test cases.

Beyond foundational gems, there are additional tools that can significantly assist in development:

6. Nokogiri - A powerful HTML, XML, and SAX parser, perfect for web scraping and data manipulation.
7. Sidekiq - A background job processing library that allows for efficient task handling and job scheduling.
8. Pry - An interactive shell for Ruby, which offers advanced debugging capabilities.
9. Active Model Serializers - A tool for creating JSON responses for APIs that improves data structure and readability.
10. Rake - A task management tool that allows developers to automate various tasks, including testing and building.

Optimizing your Rails application for performance is crucial for ensuring a smooth user experience and maintaining server efficiency. One of the first steps you should take is to profile your application to identify bottlenecks. Use tools like RubyProf or Rails Performance Testing Guide to analyze where time is being spent in your code. Once you identify slow components, you can use techniques such as caching, database indexing, and optimizing queries to enhance performance. Implementing fragment caching and page caching can significantly reduce load times by serving static content rather than rendering it dynamically each time.

Another key area to focus on is the use of background jobs to handle long-running tasks. By moving tasks that do not need to be executed in real-time to a background process, such as using Sidekiq, you can improve the responsiveness of your application. Additionally, consider using a content delivery network (CDN) to serve static assets more efficiently. CDNs can greatly reduce latency by caching content closer to users. Monitoring performance continuously with tools like New Relic or APM can help you maintain optimal performance over time as your application scales.