What are the syntax of the urls which makes it possible to target and reach the bases of data and information hidden in the depths of the invisible web ?
First of all, I'm assuming the invincible web you're referring to is the deep web.
The invisible or deep web is not indexed by search engines so you have to know the URL you're targeting. Reaching hidden data is possible by knowing which URL to target and the parameters to search for.
Most deep web sites use syntaxes like
You can target specific data or information by adding a query to the URL scheme for example
You can also target specific data by adding a fragment to the URL scheme usually an ID like in the example below.
Other that this, if you have a login to the URL you're trying to access like FTP, you can access all the files accessible by the ftp account.
I hope that answers your question.