In web projects, the designers, developers and the customer are taking huge efforts to make sure that almost literally every pixel on the web page is where it should be and this is very important. While the website gets maintained, both by adding new content and by further developing the system, either with new features or by correcting errors, it is likely to happen that something is going to be presented differently from what had been signed off before. Not only is this one of the most annoying errors and the developers often get a bad reputation in the eyes of their customers, they can also be avoided by utilizing presentation tests. That way an automated system will take screenshots of all the relevant parts of a website and store them as a reference for future comparison. This allows automation tools to automatically run the tests again and compare those same areas with the result of the signed off version and if there are differences recognized, the developers get notified. They can then decide if the recognized changed has been intended, then the new version gets stored as the new reference, or they are not, then it needs to be fixed and tested again, until it matches the result of the previously stored reference.
A proxy is either hardware or software that receives the requests from the internet and analyses the nature of that request to decide where to send that request in the internal network and also managing to send the correct response from internal services back to the original requestor.