RF24 Library: Driver for nRF24L01(+) 2.4GHz Wireless Transceiver

Big thanks for this amazing libary, at the momment I already tried all the examples included, and even made some modifications.

I want to go further but there are some basic concepts I miss, tried on google, in the main site, taking closer look to the examples, but nothing, I just dont understand some things. I really want to go deeper but I feel a good tutorial is missing. Here are some of the things I dont get.

Whats a pipe? How it changes if I want 2 or 6 nodes to speak.

const uint64_t pipes[2] = { 0xF0F0F0F0E1LL, 0xF0F0F0F0D2LL };
What the numbers mean?

Maybe after the explanation, I will figure how to solve the next issue, but just in case; How do I need to set the pipes if my network is static 6 nodes, one base. The nodes some times send data to the base and then the base answers with some other data back to the emiting nodeā€¦

Thanks for any help!