can anyone explain me, what "weak pullups" on PIC µC do mean ?
i have very basic understanding of pullups, but i cant understand its use
in PIC. what will happen if i leave them disabled or waht will happen if i enable them ?
You can use weak pullups enabled to read from keys. You will get lower noise pickup on long leads if you use lower external values, around 2k2 - 4k7 is about right. Choice is yours, will probably be ok on internal.