This is a 2-part bug-fixing exercise. First, there is an index.html page, using 'vanilla' javascript. Open it up in your browser, and the page will have instructions on how it should work and what needs to be fixed. Be sure to open up the console, as we want to eliminate any errors or misbehaving logs there.
Next, there's a react app in a subfolder. It is also full of bugs, begging to be fixed. Start by fixing the errors that prevent it from rendering a page at all - then the page itself will have more instructions on what features are still broken.
Now go flex those debugging muscles!
Don't worry about the handlebars.js file. Handlebars is a template library that's being used for displaying the results from a get request to github, but you don't actually have to know how to use handlebars to fix any related bugs.