jakazorz I meant that file will help to render code you added in the 'custom code' section in template, you can see some tags like:
{t4:system_advancedCodeAfterHead}
{t4:system_advancedCodeBeforeHead}
{t4:system_advancedCodeAfterBody}
{t4:system_advancedCodeBeforeBody}
And if you want, you can add the custom code directly into this file.