How to insert specific elements in common page content?

Very thank you both guys! Yes I have tried this options too and just need to be sure if I all doing right less or more

I dont know about usual CMS systems like Joomla or Wordpress, and I wonder how they do this, so thats why I asking here.

All this problem just because user (important that this is will be only ADMIN) must insert any specific staff(not plain HTML tags and text) in any place on the page.

For all this things I have created gallery list, google map list (cause insert google map in texteditor with custom markers unreal) and so on.

I wanted just to be sure that I am not crazy and folowing more or less in right direction

Maybe you know about some already done solutions on the webwide or hear where this is all I could read to understand better, like best practices for this kind situation?

Anyway if not, its ok. I am very grateful for sharing you expirience and ideas and I already have a clue about this

Thanks again