How to work with Bitrix documentation?

Question

CMS

I know that you need to write this question on the official Bitrix forum, but something is so sluggishly answered there that I decided to duplicate it here. Here the people are somehow more active.
At the moment I'm just learning 1сbitrix. I got to the question of components, their settings, customization. So, working with a component template implies knowing the various variables, arrays, keys, etc. associated with the component. For example, a link to the "detail" page $arItem["DETAIL_PAGE_URL"] (just an example).
Where can I find a description of all keys like DETAIL_PAGE_URL? Where to find variable declarations: $arItem, $arResult, etc. Of course, I can guess the meaning of some of them myself. For example, foreach($arResult["ITEMS"] as $arItem) - I understand that all the news, etc. are sorted here. But is there any documentation or not? I crawled through the entire Bitrix site, knowledge base, etc., but didn’t really find anything. The site is such a mess that mom do not worry. Where are those is the documentation kept? How do I work with components, is there any general documentation on components or private on specific components (news, shopping cart, etc.)? Tell me, experienced developers!
For example, through google I managed to find this https://dev.1c-bitrix.ru(but how to get here from the Bitrix website, I still did not understand in which section this documentation is stored ...). In this documentation, I went to the "components" > "news" section https://dev.1c-bitrix.ru/user_help/content/iblock/... but I did not find a description of the same "DETAIL_PAGE_URL" key in the text. if you use the search there, then as a result you will receive links to sections in which the entered key phrase occurs. By clicking on the link, you find yourself on a page that does not have breadcrumbs or a normal title, i.e. It's not even clear what section of the help you are in. How to work with such documentation - I do not understand.
Either I'm so dumb, or Bitrix has such a crooked documentation.
By the way, I did not find a description of what $arItem or $arResult is...

Answer 1

https://dev.1c-bitrix.ru/api_help/ Have you been here?