ED, ED II, and rolling admissions?

I’m pretty confused about how exactly ED works. I know it’s binding, but can you apply to other colleges early as well, given that the colleges have rolling admissions?

You really need to read the web sites of each school to understand the specifics of each school but in general:

A student may apply Early Decision to only one institution. (from UPenn’s web site)
Most ED schools will allow you to apply freely to any EA, rolling or RD school.

SCEA (Singel Choice EA) or REA (Restricted EA) generally don’t allow you to apply ED anywhere but you aren’t tied to them like an ED school. You may not be allowed to apply to a private school EA but may for a public U.

Rolling is good with every school. Go ahead and do it.

Some schools also have an ED2 deadline which is available if you are rejected by an ED school or moved to RD (deferred).

I don’t see how any EA/ED/SCEA program can prevent you from applying to a rolling school. The rolling schools are all regular decision but they make their regular decisions on a rolling basis. How can you be penalized for that?