While I am studying the Magento Basic Tutorial, there is a question confused me.
I noticed that in the /template/page/html/header.phtml rendered a child block called 'topSearch'.
<?php echo $this->getChildHtml('topSearch') ?>
However, I opened the layout associated file (page.xml), that child block was not defined under the header block. And my understanding from Magento documentation Layout Chapter, that child block would not be rendered.