Staff engineers taken on a broader and more long term scope of responsibility. Projects can involve multiple technologies and be on the timeline of years. Additionally, the people aspect is more important than a senior engineer: mentoring, communicating, etc. You'll be looked to for guidance but don't expect yourself to be a subject matter expert in everything. Instead, you'll be more successful if you delegate work out or ask others for their expertise. Knowing when to say, "I don't know" and then quickly coming to another solution is an important skill.