What's difference between bulb fibre and ordinary compost?

While I was grabbing garlic from my local Wyevale, I grabbed a few hyacinth bulbs as well to plant inside. Can I use normal compost or does it have to be bulb fibre? Or can I mix compost with perlite or something like that?

And on the subject of garlic - I spotted some called Marco, which I'd never heard of before, but they did look really nice big bulbs so I thought I'd try them. Anybody grown this before? It doesn't even say on the pack whether they're hardneck or softneck.

Bulb fibre has charcoal added. Forced bulbs are often planted in bowls with no drainage and the charcoal keeps it from rotting.

Marco is a softneck garlic.