A LookML developer is responsible for building and managing data models using Looker's proprietary language, LookML. They translate business needs into technical specifications, create customizable and reusable data models, and ensure data accuracy and consistency. They are involved in designing data architecture, maintaining databases, and optimizing data retrieval. They also troubleshoot data issues and work closely with data analysts and stakeholders to deliver insightful analytics. Their role is crucial in enabling data-driven decision-making by providing access to reliable and understandable data. They need to have strong SQL skills, experience in data modeling, and understanding of business intelligence tools.