I downloaded MAMP and set it up, and i was curious, when it syas localhost:8888/MAMP/?language=english

I understand that is my local host computer and i can only to view. But what if i want to show someone else my work from my computer? What would i put... i know it's probably myip:8888 i just wanted to make sure because i tried and it didn't work and i had troublue before with apache configuration/router type stuff and i am trying to get down to the problem of why i can see it locally but not see it externally (i once got it to work for 10 min then i moved my router/modem and computer downstairs where they shoudl be) and it stopped working... so i assume it's my router but i wanted to make sure. Thanks. Also what port would i open for port forwarding to get the website tow ork 8888 or 80?