Selenium is an open-source automated testing tool used for web application testing. Here are some of the pros and cons of Selenium:

Pros:

Cross-platform compatibility: Selenium can be used with different operating systems and web browsers, making it a flexible tool for testing web applications.

Supports multiple programming languages: Selenium supports various programming languages, including Java, Python, C#, Ruby, and JavaScript, making it easy for developers to use the language of their choice.

Open-source: Selenium is a free and open-source tool, which means that it is available to anyone who wants to use it without any licensing fees.

Supports a range of testing types: Selenium supports different types of testing, including functional, regression, and acceptance testing.

Extensible: Selenium is an extensible tool that can be integrated with other testing frameworks and tools, making it more powerful and versatile.

Cons:

Steep learning curve: Selenium can be difficult for beginners to learn, especially if they have little or no experience with programming.

Limited support for mobile testing: Although Selenium can be used for mobile testing, it has limited support compared to other mobile testing tools.

No built-in reporting: Selenium does not come with built-in reporting features, and developers must integrate it with other reporting tools to generate reports.

Maintenance can be time-consuming: Maintaining Selenium scripts can be time-consuming, especially when web applications undergo frequent changes.

Limited support for desktop applications: Selenium is primarily designed for testing web applications and has limited support for desktop applications.

Overall, Selenium is a powerful and versatile tool for web application testing that comes with some drawbacks, particularly in terms of the learning curve and maintenance requirements. However, its open-source nature and support for multiple programming languages make it a popular choice among developers. For details, You can even check concepts of Selenium through WebDriver, Grid, IDE, handling IFrames, Alerts, and Modal Dialog box with the Selenium Course.