A Junior Web Application Developer assists in designing, coding, and maintaining web-based applications under the supervision of more experienced developers. They typically work with programming languages like HTML, CSS, JavaScript, and backend languages such as Python, PHP, or Ruby. Their responsibilities often include fixing bugs, implementing new features, testing code, and collaborating with other team members to ensure the application meets user requirements. This role is ideal for those starting their career in web development, as it provides valuable hands-on experience and opportunities for learning.