Sorry for this lame question but I have been going active for my whole life.
Installed passive pups yesterday and connected it to my amp before putting on any strings .. It just bzzzzzzz loud. Then I put on a string and no bzzz at all...
I suppose it should be like this because of the ground but I just want to make sure I did it right =) Hope someone can tell! Thanks!
The strings are indeed an important part of the ground scheme in most guitars. Some active pickup wirings don't ground the bridge but that's a different story.

If it went away when you put strings on, there's nothing to worry about.
Thanks Roc! So then the grounding is perfectly normal as everything sound and work as it should when the strings are on, right ?
Thanks Roc. =)
To make really sure I will pick up a friends guitar with same pickups tomorrow and compare their behaviour with and without strings too! =)
Borrowed my friends guitar with "fabric" soldered (same pups). They act/sound the same so all good =) Thanks again!