I have observed many apps that show HTML such as Chrome and Steam have these 'helper' processes. These processes have been taking up insane amounts of RAM on my Mac. Applications such as Steam and Chrome will take up gigabytes of RAM. Most third party applications that have a helper process tied to it will render the computer unusable, and I'll have to reboot. The Unity Asset Store alone, when it's window is opened, takes up almost a gigabyte of RAM.
My Mac is running macOS Sierra, which you would think is the problem since it's a Beta, but the problem was present in earlier versions of OS X since Yosemite.
Best Answer
With many of these 'multi-page' applications like web browsers, each open tab or window gets its own 'helper' app, which supports that open web page.
The only way to clear them is to close unused tabs.
For such as Steam or Unity, the helper app will be the one actually supporting & running the loaded game etc. The 'face' app/portal will just be running itself.
Example of 'greedy' web browser in action... The 'total' figure shown for Safari itself does not include the other sub-process below, they are in addition to Safari's own memory usage.