Welcome to the Raspberry Pi community of Stack Exchange.
Any "normal" USB keyboard that you might use with a (say) Ubuntu {I see you are in other SE communities including that one} PC should work for you - the Raspbian distro is derived from the Debian one of the same version ("Jessie", although older ones were previously used).
As per Debian, the change from "Wheezy" to "Jessie" marked a switch from sysV init
to systemd
"by default" but from an OS point of view you could find yourself fairly at home on a Pi, IMHO!
The boot-up process is (a little) different, as you spotted there is not a BIOS, instead the NOOBS system occupies the first (VFAT) partition on the SDCard and that normally switches to whatever you have chosen in one or more of other partitions. For Raspbian and other distributions the /boot
part of the eventual filesystem contains config.txt and cmdline.txt which play a special part in how your system operates.
Compared to a PC Distribution there are extra libraries and stuff to work with the General Purpose Input Output (GPIO) bus which is that row of pins that look like what you might plug an IDE HDD connector cable into (don't do that) - instead that is what you use to attach a wide variety of hardware both ready-made and things you can build yourself to do all sorts of things with.
The Pi does seem to have 4 USB 2.0 ports however there are limits to the power that attached devices can draw - usually for the power hungry things you will need to use a powered USB HUB for things like external HDDs should you wish to use them.
The Pi 2 that you have is indeed a quad-core {ARM7} processor (running at around 1GHz) IIRC with 1GB of memory separately on the PWB - the GPU is also included inside the same package. Earlier Pis had a single processor with the same GPU and 0.5GB (or 0.25 on very early ones) and ALL of that was squeezed into two ICs packaged "one-on-top-of-the-other"!
This only touches the surface of what you have just got - so hang around here for a while, ask good questions (use the search box on the top right corner of the screen to avoid asking questions that have already been asked many, many times before), and enjoy your Christmas present!