Answer 1

Pu to put it simply is an unofficial tier made out of Smogons least used NU Pokemon.

PU (What does this even stand for) are the Pokemon that even NU doesn't want, basically Pokemon that have less than 3.41% usage in NU are technically "PU". In PU, some Pokemon - otherwise regarded as bottom of the barrel - could become top tier threats. With the Pokemon ranging from lovable Luvdisc to the raging Rampardos, it's your job to find out which Pokemon and strategies dominate the tier (like VolTurn in OU).

http://www.smogon.com/forums/showthread.php?t=3467083
Here is an example team

Answer 2

It's not a real tier, but one made by Smogon. It's for Pokemon that are not used very often in NU. So basically it's the NU of NU. This link should help a bit

Comments

Your link doesn't work :D
From going into edit it shows you don't have a correct url

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oh tnx for telling ill fix it