A more junior developer tends to be inward looking - they are most concerned with completing the ticket they are working on at any one time.
A more senior developer tends to become more outward looking. This comes in a few different forms. First, they play a greater role in mentoring their peers and other members of the team. They become a force multiplier for those around them. Second, they play a larger role in interfacing with other teams. For example, they may communicate with the commercial team on delivery of certain features or they may communicate more with management. Third, they play a bigger role in improving the team itself e.g. suggesting improvements on management of the sprint. Finally, they may contribute towards management of others and hiring.
Different Types of Senior
Importantly, a senior developer won’t necessarily cover all these arcs. Different people have different traits and preferences which will allow them to excel in different areas.
For example, you may have a developer who excels at designing systems, is highly independent, is a voice of authority on products but is otherwise happy to stay away from hiring, management, mentoring or communicating with other teams.