After reading some interesting manual of Octopoos regarding content type storage, I also checked up on how to use Joomla categories and Tags wisely. This is for structuring my site the good way...

Then I tested SEBLOD, because in the piece Octopoos wrote it was strange for me to understand we can only create content type based on either (Joomla) Article, User or Category:

But I really do not see any difference between creating a whole new content type or choose one based on article.

So I created:
content type name : jobopening (based on article)
content type name : custom-jobopening (based on app folder I made, so blank)

(Both automatically sets com_finder on intro. I did not try content yet. But that's probably not of issue.)

In bothe I added one created text field (education) and in both added fields from a normal joomla article : title, alias, category_id.
I created two articles (seblod) and one was new content type (custom-jobopening), one was based on article content type (jobopening),
For both I choose a Joomla category (created with Joomla, and not SEBLOD!
I created a Joomla menu based on the category I had chosen when I made the article.

Both are displayed.
Then I also searched with normal joomla searchbox on : title, category and even the custom field value, and custom field label.
All gave me the exact article!

So, I am also not sure what exactly SEBLOD search menu is for?

ps.
I checked my Joomla content table and did notice the SEBLOD tags are inside the intro-text column.
I checked if there was a cck_store_form_jobopening, and it had one: the one based on the joomla article.
I really would not know where the totally custom one (custom-jobopening) went?!

I think tomorrow I will do some testing on tags.