A “Javascript unit test runner”. This means that Karma executes unit tests, written in javascript.

This happens as following:

• Start up a NodeJS
• Launch the real browser via a browser launcher
• Execute JavaScript code on the NodeJS browser and check the results.

Only UNIT TESTS are executed here - means only separate functions will be executed, no complete applicaiton is executed.

Compared to that protractor executes the application and runs the tests against it. (End-To-End tests)