This chapter focuses on key concepts in that literature regarding grammar, functions, and Code-switching (CS) issues in psycholinguistics. It discusses the advantages of an interdisciplinary approach to CS. CS occurs naturally across language pairs and in distinct political and geographic contexts where languages are in contact. The literature on CS and bilingual competence has offered important insights about the grammatical dexterity of code-switchers. Sociolinguistics research has informed us extensively about the social and pragmatic purposes for CS. Sociolinguistic research in diverse geographical and political contexts has offered insights as to the social and identity factors that may influence CS among bilinguals. The research on CS within psycholinguistics is an emerging area of study compared to CS studies within sociolinguistics. However, CS tends to occur in more informal spaces, be it face-to-face or written informal interactions. In healthcare CS plays an important role in communication.