A minecart with hopper will travel along rails like any minecart; however, any nearby items will be pulled into its inventory. It will also pull items from storage above itself; however, it does this 7.4 times faster than a regular hopper, which will push items into the hopper minecart if its orientation is correct. While a minecart with hopper will not push items into containers, hoppers will pull items from any hopper minecart that it can.
If a minecart with hopper goes over a powered Activator Rail, it will lose its abilities, and if it goes over an unpowered activator rail, it will regain its abilities. The exception is that hoppers can still push and pull items to and from a minecart with hopper. When it is on a Detector Rail, a Redstone Comparator can detect the cart's fullness the same way it detects the fullness of a regular hopper.
|Minecart with Hopper|