Traditional item recommendation systems ingest user historical behaviours and predict items of interest to their users. Recommendations can then be fed back to the users. The latest generation of large language models (LLM) can generate high-quality text, can follow detailed instructions, and can access a wide amount of information (encoded in their weights and through retrieval mechanisms). These characteristics enable both new ways to learn user information (i.e. through user-generated instructions or prompts) and new ways of modeling user representations (i.e text-based user representations or personalized recommendation justifications).