What is the difference between "liege-vassal" and "simple vassal"?

Question

Jean Bodin said in his Six Books of the Commonwealth:

The fourth is the simple vassal who owes faith and service for his fief, but is neither a sovereign himself, nor the natural subject of the man of whom he holds the fief. The fifth is the liege-vassal of a sovereign prince but not his subject.

The liege-vassal owes obedience to his lord in relation to and against all. The simple vassal reserves the rights of his lord's superior.

But I didn't understand Bodin's explanation of the difference between these two types of vassals.

Answer 1

Via Expectations of the law in the middle ages

A liege vassal was somebody who was completely his lord's man

Via Galbert of Bruges

a vassal who will serve his lord before all others

By comparison, a simple vassal is a vassal in the traditional sense: of the king first and foremost, then perhaps to one or more dukes or counts under the king (or as the case may be, to multiple kings!). His loyalty to the duke above him only extends as far as his land within that duke's realm.

Both are distinct from a subject, who in Bodin's definition is inherently beholden to a lord, whereas vassals of both kinds only owe this fealty while they hold the lord's fiefs that they have been entrusted with.