How to know MAC address ( Machine address)??

Can I change it?

ping it, run arp -a and match the IP address to the MAC address.

if you want to change your MAC address in linux
ifconfig ethX hw ether <mac address>

I don't understand it clearly
I want to know my MAC address and Must I ping my IP address?
my IP address is 161.XXX.18.Y1 so I use this command

[root@localhost root]# ping 161.XXX.18.Y1
and when I run " arp -a"
[root@localhost root]# arp -a
? (161.XXX.18.4) at 00:0B:CC:CC:CC:CC [ether] on eth0
? (161.XXX.18.1) at 000DDD:CC [ether] on eth0

I use both command "ping" and "arp -a" in the same machine?
what does it mean?
why don't have my IP address "161.XXX.18.Y1"
The machine that have IP "161.XXX.18.4" ping to me?
and if I ping to one machine,and doesn't want that machine know I ping to.. How to delete it? I mean when that machine use command "arp-a" and my IP disappear...

How to change MAC address in Window?
and the last questions Could u explain me more about command "arp-a"?

arp -a just lists the contents of the arp cache.

you best off just using ifconfig -a to get up the mac address.

dare i ask why you're changing the mac address?