Expressivism is a broad family of views claiming some areas of discourse are ‘in the business’ of giving expression to sentiments / commitments / non-cognitive or non-representational mental states or attitudes.
German tradition began with Herder (1744-1803, a student of Kant) who advocated global anti-representationalism: all language is (primarily) expressive, rather than representational.
Another tradition is 20th century meta-ethical expressivism. Some vocabularies (e.g. moral) for which the representational model is not appropriate. First-wave expressivists were A. J. Ayer. Geach’s argument created a new criterion of adequacy for expressivists, and the ones who responded to this (e.g. Simon Blackburn and Gibbard) are second-wave expressivists.
About truth
Expressivism about truth is to say one is not describing a statement when one says it is true - one is doing something else (endorsing it). Combining this with universal declarativism about truth leads to global anti-representationalism / anti-bifurcationism
Expressivists who want to equate the semantics ”” and “It is true that ” are only considering free-standing uses of . The Frege-Geach argument demands emotivists to also consider embedded uses of ,1 thus disquotationalism / prosentential theories are required to show how embedded uses of derive their meaning from free-standing uses of it.2