Selenium automates browsers. That's it! What you do with that power is entirely up to you. Primarily, it is for automating web applications for testing purposes, but is certainly not limited to just that. Boring web-based administration tasks can (and should!) also be automated as well.
Selenium is a tool in the Testing Frameworks category of a tech stack.
What are some alternatives to Selenium?
BrowserStack is the leading test platform built for developers & QAs to expand test coverage, scale & optimize testing with cross-browser, real device cloud, accessibility, visual testing, test management, and test observability.
Karma is not a testing framework, nor an assertion library. Karma just launches a HTTP server, and generates the test runner HTML file you probably already know from your favourite testing framework. So for testing purposes you can use pretty much anything you like.
LambdaTest platform provides secure, scalable and insightful test orchestration for website, and mobile app testing. Customers at different points in their DevOps lifecycle can leverage Automation and/or Manual testing on LambdaTest.
WebdriverIO lets you control a browser or a mobile application with just a few lines of code. Your test code will look simple, concise and easy to read.
Nemo.js, Selendroid, Targetprocess, Nightwatchjs, Zen Rails Base Application and 7 more are some of the popular tools that integrate with Selenium. Here's a list of all 12 tools that integrate with Selenium.