Retrofit vs Shields.io: What are the differences?

## Introduction
This Markdown code compares the key differences between Retrofit and Shields.io.

1. **Programming Language Compatibility**: Retrofit is a type-safe HTTP client for Android and Java, primarily used for creating REST API services, while Shields.io is a service that allows you to create custom badges for your projects in various programming languages such as HTML, Markdown, etc.
2. **Service Type**: Retrofit is a client-server type of service, where it interacts with web services and APIs, while Shields.io is more of a design service that generates badges to add to the visual appeal of your project's documentation or README files.
3. **Customization Options**: Retrofit provides extensive customization options for HTTP requests and responses, allowing developers to fine-tune the client behavior according to specific requirements, whereas Shields.io offers customization in terms of badge styles, colors, and data to be displayed on badges.
4. **Integration**: Retrofit is typically integrated into Android or Java projects to handle network requests and data retrieval from APIs, while Shields.io is integrated into project documentation or README files to display badges related to build status, version, activity, etc.
5. **Dependency Management**: Retrofit requires adding a specific library dependency to your project to utilize its functionalities efficiently, whereas Shields.io can be directly used by generating custom badge URLs without any library integration.
6. **Main Use Case**: Retrofit's main use case revolves around managing network calls and API interactions in Android/Java applications, offering increased efficiency and robustness, whereas Shields.io is mainly used for showcasing project status, version details, and activity metrics through visually appealing badges in documentation.

In Summary, Retrofit is focused on network communication in Android/Java apps, while Shields.io enhances project documentation with visually customized badges for various status indications.