EIGRP and loopback interfaces

Hi guys,

I'm practicing for the CCNA exam and I found this packet tracer simulation where you have to set up 2 EIGRP domains, one for IPV4 and one for IPV6, each with his loopback interfaces.

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I've successfully configured them to be advertised with a classfull IP that would include them all as the test demanded, but I did kind of "mechanically", I can't wrap my head around it since all the EIGRP I've done so far was without them, just advertising the network attached to each interface with the command "network IP WILDCARD"

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Google didn't help much, can someone please explain to me like I'm five the relationship loopback interfaces and EIGRP?

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Thank you so much, help a network rookie please :)