What is the difference between חרמין וההקדשות?
Since they are both making something the property of the Temple Treasury
(actually there is a machlokes between Rashi and Tosfos see Rosh Hashana 4a)
In Rosh Hashana 4a (on the bottom in the braisa) mentions both of these things.
What is the difference between them?
Maybe something in Halacha?