Instance metadata is data about your instance tah you can use to configure or manage the running instance

[root@ip-10-192- ]# curl http://169.254.169.254/latest/meta-data/

ami-id
ami-launch-index
ami-manifest-path
block-device-mapping/
hostname
instance-action
instance-id
instance-type
local-hostname
local-ipv4
mac
metrics/
network/
placement/
profile
public-keys/
reservation-id
security-groups

services/

[root@ip-10-] curl http://169.254.169.254/latest/meta-data/ami-id ; echo
ami-de347abc

 

[root@ip-10-192-10]# curl http://169.254.169.254/
1.0
2007-01-19
2007-03-01
2007-08-29
2007-10-10
2007-12-15
2008-02-01
2008-09-01
2009-04-04
2011-01-01
2011-05-01
2012-01-12
2014-02-25
2014-11-05
2015-10-20
2016-04-19
2016-06-30

root@ip-10-192]# curl http://169.254.169.254/latest/meta-data/public-keys/0/openssh-key

Check public IP behind NAT

[root@ip-10-192- ]# wget -qO- http://ipecho.net/plain ; echo
50.18.yyy.yy