~site/_layouts/15/osssearchresults.aspx?u={contexturl}

Hi,

I have the following URL in my  Search Box Web Part - Results Page URL -

~site/_layouts/15/osssearchresults.aspx?u={contexturl}

Although I can guess what {contexturl} means, I wonder if there is any documentation that explains the {contexturl} variable and all the similar variables that I can use in SharePoint web part properties.

Thank you