Hi Shaliya - Welcome to TamaTalk
PM means Personal Message. Have a look at the bottom of my reply screen and you'll see small buttons with SEND PM or SEND EMAIL (for example) on them.
SEND PM will allow you to compose a PM to the person who has posted that reply.
I will move this questions out of the Introductions section and put it into the Help for New Tamagotchi Owners section. That way more people will see it - and anyone else who doesn't know what a PM is will also get their question answered :furawatchi:
Best, etc.
TamaMum