eigrp spins up...

and it learns a couple of things without benefit of input from other routers, yet..

in other words local information

subnets that it can add to its eigrp process before being bothered by neighbors...

prefixes from interfaces that have been enabled with the network command in its router configuration

and

prefixes learned from redistribution from other routing protocols

now it is prepared to send meaningful updates to its neighbors using five kinds of messages:

hello
update
query
reply
ack

updates contain:
prefix
prefix length
metrics primarily bandwidth and delay (reliability and load?)
non-metrics mtu, hop count

dls1#sh ip eigrp topo 172.16.1.0/24
EIGRP-IPv4:(1) (AS 1): Topology Default-IP-Routing-Table(0) entry for 172.16.1.0/24
  State is Passive, Query origin flag is 1, 1 Successor(s), FD is 2816
  Descriptor Blocks:
  0.0.0.0 (Vlan1), from Connected, Send flag is 0x0
      Composite metric is (2816/0), Route is Internal
      Vector metric:
        Minimum bandwidth is 1000000 Kbit
        Total delay is 10 microseconds
        Reliability is 255/255
        Load is 1/255
        Minimum MTU is 1500
        Hop count is 0
  172.16.100.2 (Vlan100), from 172.16.100.2, Send flag is 0x0
      Composite metric is (3072/2816), Route is Internal
      Vector metric:
        Minimum bandwidth is 1000000 Kbit
        Total delay is 20 microseconds
        Reliability is 255/255
        Load is 1/255
        Minimum MTU is 1500
        Hop count is 1
  172.16.200.2 (Vlan200), from 172.16.200.2, Send flag is 0x0
      Composite metric is (3072/2816), Route is Internal
      Vector metric:
        Minimum bandwidth is 1000000 Kbit
        Total delay is 20 microseconds
        Reliability is 255/255
        Load is 1/255
        Minimum MTU is 1500
        Hop count is 1
dls1#