So you want to buy a domain name with the extension .fr?
Everything is not allowed, as this extension is only available under conditions. In fact, to make up for cybersquatting and to allow a better representation of the French cities and communes, they are entitled to buy them first.
Once the domain is reserved, they have to send a paper document (the DOA, which stands for AFNIC operations request) with the necessary evidences to allow its releasing.
If, as a private individual or other entity, you want to buy a .fr domain name, you should check first if no French commune is named like the domain you would like, as you will not be able to get it in that case. Here is a list of French communes to help you out.
Nom de domaine en .fr (in French)
Nombre de dominio en .fr (in Spanish)
Nome de domínio en .fr (in Portuguese)