Help with parts identification from arduino starter kit from aliexpress Ordered an arduino starter kit from aliexpress Link

The parts list they provide (as a jpg on the order page) is vague and not very descriptive, I've gone through most of the parts and am down to three they did not list.


Capacitor? -- Looks to be a capacitor, labeled HDX and nothing else, rattles when I shake it.

Black LED -- I think this is a flame sensor; if it is, what's the difference between this and an infrared receiver (like a 1838B) or photoresistor?

They also list something as 'a digital control' near the bottom of the list, not sure what that is? Every other part from the list is matched up and I don't see anything different in the first picture (not parts list picture) from what I have received in the order.
Those are tilt sensors. The rattling is a metal ball that contacts two pins inside, closing the connection.
The 1838B is a full module that partially decodes the received IR so that a MCU can fully decode the rest easily. What you have there is a bare phototransistor with an IR window on the top. You would use it for proximity or presence sensing. Instead of varying its resistance, it varies the amount of current it will pass.
Probably the single-digit 7-segment display, as opposed to the 4-digit display they have listed as "4 digital tube".