Identifying components and there purposes on common Relay boards

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2Pringles

Joined Apr 9, 2022
33
Relays.png

:)Hey all, New to circuitry

Ive managed to identify the following components
  • Relays
  • LEDs
  • 3 pin terminal screw blocks
  • Resistors

However
In b), what are the two cylindrical drums? Capacitors? what is there purpose as they arnt present on the other five boards
In c), what is the named type of the yellow terminal block called?
In d), Just above the relays, sitting horizontally, are they parts labelled R1, R2, R3, resistors, if so why are these needed?
In d,e,f) what are both the bigger and smaller square/rectangular blocks, and what is there purpose?
 
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