Hard Disc Drive Types?

[Nominus Experse]

I have decided to purchase an external hard disc drive of considerable size (1 - 2 TB).

But what I am wondering is this:
What's the difference between USB and Firewire? Firewire is faster, right? And there's 400 and 800? What exactly do these mean?


Another question I have is this:
What are the advantages and disadvantages of each particular type of internal HDD?

ATA/IDE? (This is being phased out, as I understand, due to its slower speeds, right?)

SATA (Faster than ATA/IDE, since it has a 150 speed, correct?)

SCSI (I know nothing about this type)


A few other questions I have are as follows:

What is RAID?

Is there any possible way to make my external HDD accessible to other computers through a network or some such thing?