There is no iron-clad definition other than "the country where the DVD was released". As Lewis Prothero already said: a good indicator is the rating system used on the cover. More info on various rating systems can be found here.

It is not uncommon for a release to share several locations. This occurs frequently for e.g. the following combinations:
- UK and Ireland
- Netherlands and Belgium
- Scandinavian countries.
In such cases, both localities can be legitimate, provided the localities' languages are in use on the cover.

In your case, I would say: check if the rating system on the cover is the Dutch-Belgian rating system (for DVD and Blu-ray releases, the two countries are sharing the same system). If that is indeed the case, then given the fact that the Overview is in French, you can be pretty sure Belgium is the correct Locality.

There are also pan-European releases - this is e.g. quite common for music DVDs. Many of these have both a German (FSK-0) and a UK (E) rating on their covers. These releases can be sold anywhere in Europe, but because of their ratings I am always inclined to contribute them with either Germany or UK as their locality.

What about upc 8712609665932?

2 identical Netherlands and Belgium versions (and there are lots of them). In this case I would say Belgium since the language is Dutch/French and they don't speak French in The Netherlands, only in Belgium Dutch and French are official languages.

Quoting Jsco:

Quote:
What about upc 8712609665932?

2 identical Netherlands and Belgium versions (and there are lots of them). In this case I would say Belgium since the language is Dutch/French and they don't speak French in The Netherlands, only in Belgium Dutch and French are official languages.

It appears this release was intended for two markets / countries; both the Netherlands and Belgium.

Notice on the cover is bilingual and has both a NL and a FR overview.  It also lists SPHE.NL and SPHE.BE as the websites on the back cover.  Thus this release can be added with the same UPC but two different localities.

Now, it's also common for Denmark, Finland, Norway, and Sweden (i.e. localities) to share the same release.  Let's take EAN 5051895051658, Inception Blu-ray, as an example.  This release has an overview for each of the four countries along with the country flags and country ratings.  Now, this EAN uses a 505 prefix which means the UK division of WB handled this release for the Danish, Finnish, Norwegian, and Swedish markets.  Thus this EAN can be added four times once under each of the four localities.

See back cover here:

Inception Blu-ray

Quoting rdodolak:

Quote:
Quoting Jsco:

Quote:
In this case it says www.warnerbros.be

but also

Edité et distribué par Warner Home Video Benelux, une Société de Warner Bros. Entertainment Nederland B.V.

Websites are however not a unique way of describing 'location' see upc 5051888039359.

In regards to the Fringe: Season 1 DVD it appears this is a dual locaility release; see explanation above.  This release is bilingual and has both the Dutch and French overviews as well as the Netherlands and Belgium web sites listed on the back cover.

I see that the database only has it listed for the Netherlands locality though.  This just means that someone didn't take the time to contribute it for the Belgium locality.

An administrator must have removed the Belgian entry. This morning I had 2 items for this upc (Netherlands and Belgium), now only 1. So probably that means that there shouldn't be duplicates in the database.

Quoting Jsco:

Quote:
And I don't really care what location I enter, just want to know the definition, since it is not in the 'Contribution Rules' and apparently it does matter since I got a profile deleted because of it.

Yeah. Sadly we have a small number of users here who appointed themselves the cleaners of the database and contribute "to be removed" profiles if they feel they shouldn't be in that locality.

Doesn't mean they're right though.

Quoting Jsco:

Quote:
What about upc 8712609665932?

2 identical Netherlands and Belgium versions (and there are lots of them). In this case I would say Belgium since the language is Dutch/French and they don't speak French in The Netherlands, only in Belgium Dutch and French are official languages.

Both NL and B are legitimate localities here, as I already explained. The only difference between both profiles should be that in the NL profile the French Overview should be omitted per the contribution rules.
I already told you that combined NL/B releases are very common and that there's nothing wrong with that.

Quoting marcelb7:

Quote:
Quoting Jsco:

Quote:
Quoting rdodolak:

Quote:
Quoting Jsco:

Quote:
In this case it says www.warnerbros.be

but also

Edité et distribué par Warner Home Video Benelux, une Société de Warner Bros. Entertainment Nederland B.V.

Websites are however not a unique way of describing 'location' see upc 5051888039359.

In regards to the Fringe: Season 1 DVD it appears this is a dual locaility release; see explanation above.  This release is bilingual and has both the Dutch and French overviews as well as the Netherlands and Belgium web sites listed on the back cover.

I see that the database only has it listed for the Netherlands locality though.  This just means that someone didn't take the time to contribute it for the Belgium locality.

An administrator must have removed the Belgian entry. This morning I had 2 items for this upc (Netherlands and Belgium), now only 1. So probably that means that there shouldn't be duplicates in the database.

The Belgian locality of Fringe: Season 1 has never been contributed to the database. Check http://www.invelos.com/Forums.aspx?task=contributionnotes&type=DVD&ProfileUPC=5051888039359.30.

Dammit, I mentioned upc 8712609665932, that is Breaking Bad S1. Don't know why al of a sudden we were talking about Fringe.
Anyway, I got Fringe 1 too. Do I understand correctly that I can add it as a Belgian entry although it is exactly the same. If that are the rules, its fine to me but it sounds strange.

There's nothing strange about this from the perspective of media companies being able to serve several interrelated markets through a single release. DVDP rules merely reflect that reality.