What are Ancillary assets?

When ancillary estates are opened, the estate is viewed separately from the primary estate.  

The primary estate consists of assets tied to the state where the decedent was a resident and any non-state-specific assets (such as bank accounts). The ancillary estate consists only of the assets tied to the estate where ancillary probate was opened (often physical assets). 

Since ancillary probate is based on just the assets in a certain state, it is possible for an ancillary estate to qualify for simplified procedures (assuming the procedure allows for ancillary assets). Primary probate is typically kept open until all ancillary cases are closed since the ancillary cases are usually contingent upon the personal representative having been appointed in the primary state.