Giftrain is adware and a Potentially Unwanted Program. If the user is seeing pop-up ads from Exclusiverewards.giftrain.eu whenever they open a new tab within Internet Explorer, Firefox or Google Chrome, they probably have the adware on their PC. It can be removed using AdwCleaner, Malwarebytes Anti-Malware, and HitmanPro.
The program is designed specifically for the creator make money. It generates web traffic, collects sales leads for other dubious sites, and will display advertisements and sponsored links within the user's web browser, which is usually annoying.
Usually the Exclusiverewards.giftrain.eu pop-up will promise the user a prize (eg: iPhone, iPad, MacBook Air or another product) if they complete the survey. However, in reality, these cyber criminals will get some sort of revenue for each survey the user completes.
Exclusiverewards.giftrain.eu is not a malicious domain itself, but it is a survey scam. Cyber criminals are using an adware program to display ads from this domain, thus getting pay-per-click revenue.
The user should always pay attention when installing software because often, an unknown software installer includes optional software, which can include malicious programs and adware.