Repeater allows for slight changes or tweaks to the request, and it is displayed in the left-hand window. A Go button allows the request to be reissued, and the response is displayed in the right-hand window.
Details related to your HTTP request include standard Message Editor details such as Raw, Params (for requests with parameters or cookies), Headers, and Hex.
Details related to the HTTP Response include standard Message Editor details including Raw, Headers, Hex, and, sometimes, HTML and Render.
At the bottom of each panel is a search-text box, allowing the tester to quickly find a value present in a message.