Form of life (German: Lebensform) is a term used sparingly by Ludwig Wittgenstein in posthumously published works Philosophical Investigations (PI), On Certainty and in parts of his Nachlass.
[1] It is a term widely understood to refer to the shared background of human cultural practices, activities, and ways of living that provide the context within which language and meaning operate.
Wittgenstein in his Tractatus Logico-Philosophicus (TLP) was concerned with the structure of language, responding to Frege and Russell.
Leading up to a revised view in his PI, still concerned with language, but now focusing on how it is used and not insisting that it has an inherent structure or set of rules.
Italian philosopher Giorgio Agamben doesn't take Wittgenstein's concepts in his analysis of the history of Western monasticism in order to rethink "bare life" in contemporary (bio)politics.