Which skills do senior devs have that mediors don't? Also, which skills do team leaders need to have?

I don't know if someone who has been programming for a long time can call themselves a senior programmer if they only have a bunch of experience but won't share their knowledge with the rest of the team. What makes me a medior programmer if I can solve something even faster than the guy with the most experience in my company?

My company expects senior devs to be natural team leaders, and my team lead and the most senior developer in the company is constantly digging rabbit holes as if he weren't solving the same problems before. What do I need to improve in order to get the lead position?