[j-nsp] Eth Wan Port vs Eth Lan Port

[chenoi A]

Hai...
 
please need some explanation..
 
different between ethernet wan port and ethernet lan port. i mean can a lan port be wan port and wan port as lan port? in juniper router is it can be done.
 
if my provider connected to my router via ethernet ..can i connect to my router lan port and configured as static as my router doesnt have ethernet wan port. is this possible?
 
Thank you in advanced...