FPGA 101?

I somehow have a hard time to understand how the FPGA on the Parallella works.
What I got so far is, that it has a certain number of programmable gates and some of them are used to connect some output pins, the hdmi(?) and the Epiphany(?) and the remaining gates are free to be used for custom programming.
So one can play around with the fpga without interfering with the standard setup?
Can anyone recommend a beginners guide or a tutorial of a hello-world program with VHDL (I guess that is what is used to program the beast)?
Best regards,
What I got so far is, that it has a certain number of programmable gates and some of them are used to connect some output pins, the hdmi(?) and the Epiphany(?) and the remaining gates are free to be used for custom programming.
So one can play around with the fpga without interfering with the standard setup?
Can anyone recommend a beginners guide or a tutorial of a hello-world program with VHDL (I guess that is what is used to program the beast)?
Best regards,