We can use sort_order argument in Magento_Catalog/layout/catalog_product_view.xml xml config as described below:

<referenceBlock name="product.info.description">
    <arguments>
        <argument name="title" translate="true" xsi:type="string">Description</argument>
        <argument name="sort_order" xsi:type="string">20</argument>
    </arguments>
</referenceBlock>

Reference from Magento2 : Change order of Tabs on Product Page

Hope this will help.

In Magento 2.3.X, we can use sort_order argument in Magento_Catalog/layout/catalog_product_view.xml xml config as described below:

<referenceBlock name="product.info.description">
    <arguments>
        <argument name="title" translate="true" xsi:type="string">Description</argument>
        <argument name="sort_order" xsi:type="string">20</argument>
    </arguments>
</referenceBlock>

Reference from Magento2 : Change order of Tabs on Product Page

Hope this will help.