@JakeCham there are two types of content, static and dynamic.
The dynamic content changes very frequently, generally the content author authors this content. we need to send this content for translation.
The static content will not change very frequently and managed by the developer, just an example for this is placeholder text which you see in the search textbox. we cannot send this for translation because it is part of our code. We need to handle this via Java API or JS API. example: i18n.get("Search");