Google Pixel phones come with software features called HDR+. HDR+ plus was designed to improve the results you get from shooting photos. What HDR Plus does it takes short multiple exposures and combines each pixel and intelligently analyzes all of the images taken at different exposures, to help reduce noise and image blur and result in an image with an extended dynamic range.
This HDR+ shooting mode helps to capture beautiful well-exposed images when shooting in tough lighting conditions due to high-contrast scenes, rapid motion in scenes, backlight or lack of available light. The best thing about Google Pixel HDR+ feature is that it results in natural looking images, unlike some other HDR apps the produce unnatural results by boosting the contrast and saturation.
HDR isn't a new feature to Google-branded phones, some of the Nexus phones like the Nexus 6P has it. But in the Pixel phones, Google was able to improve the HDR+ feature due to the phone's superior processing power, that can now combine several RAW images almost in real time, instead of just utilizing a single image. This might result in some strong moiré in high-frequency patterns in certain areas of the photo due to the processing and alignment of the pixel from various image layers, but at the end, you get an image that is more detailed, sharp and balanced in terms of color reproduction and exposure.
The idea is to automate the analysis and optimization process of the image, instead of offering correction tools to do that (there are tons of apps for that on the Google Play store). Users just want to tap to capture an image and they want to get the best-looking image without the need to check if the image turned up ok and reshoot. So Google takes the HDR technology and pushes it a few steps forward in the new Pixel phones.
Google Pixel camera was extensively tested by DxOMark and proven to be one of the best mobile phones cameras on the market as of the time of writing, with a total score of 89. This puts it above all other smartphone cameras.