How to call category collection on home page in magento 2?

Here is open source extension for do that - you can use code and modify for your needs Magento 2 Frontend : How to call category collection on home page Explained in blog post

<?php 
  $categoryHelper = $this->helper('Magento\Catalog\Helper\Category');
  foreach($categoryHelper->getStoreCategories() as $category): 
?>
  <li><a href="<?php echo $categoryHelper->getCategoryUrl($category) ?>"><?php echo $category->getName() ?></a></li>
<?php endforeach; ?>