What's the difference beetween middle name and given name?
Middle name implies that it is constituted from names placed after the "pre-name" (
praenomen, which, as far as I know, translate as "given name") and before the family name ("the name").
Pre-name, middle name and post-name (in eastern naming conventions) are personal names, which mean that the name the individual rather than is parents (like patronymics) or his family (like family names) or a branch (like cognomens).
Contrary to having a "pre-name" and a middle name, having multiple "pre-names" and no "middle name" mean that all pre-names are part of the same part of the full name. In France, for example, someone with multiple
prénoms can chose to be legally called by anyone of them as they are all his "pre-name". That's how Henri-
Philippe-Bénoni-Omer Pétain did chose his second ranked pre-name, Philippe, as his main pre-name and was called back then just like today, Philippe Pétain. That's why Louis-
Philippe-Albert d'Orléans decided to be called Louis-Philippe (avoiding to use Albert) up to 1883 and then, only, Philippe (avoiding to use Louis and Albert).
All pre-names are equally pre-names and any of them can be used as the main pre-name. On the contrary, a middle name couldn't be used as a pre-name without ceasing to be the middle name.