Cross-platform development is the practice of developing software products or services for multiple platforms or software environments. It allows developers to create apps that run similarly on different mobile platforms 23. Here are some key points:

1. Definition: Cross-platform development aims at creating a single application that runs identically on multiple platforms. It provides the flexibility to build your app using a universal language like JavaScript which can then be exported to various smartphone platforms.

2. Comparison with Native and Web Apps: Native applications are built specifically for each platform, usually iOS and Android, with completely different programming languages. On the other hand, web apps are applications that run on the web and are not installed on the user’s device5. Cross-platform apps provide a middle ground, allowing one app to work across multiple platforms.

3. Advantages: One of the key advantages of cross-platform development is the shareable code. Having one single codebase means that mobile engineers can save time by avoiding the need to write code for each operating system, accelerating the development process.

4. Popular Frameworks: There are several popular frameworks for cross-platform development, such as Flutter, React Native, etc. For example, Flutter, released by Google in 2017, is a popular framework for building mobile, web, and desktop apps from a single codebase.

Remember, the choice of framework largely depends on your particular project and your goals.