I assume we are talking about Windows, here.
Eyefinity allows to have upto 6 monitors as one big screen (eyefinity group).
For instance, you can have 12 monitor wall but built by two eyefinity groups as extended displays. You can also use all monitors independent on the desktop or in mixed mode (some in groups, rest as independent). But not as the one logical screen in Windows.
Firepro cards allow to do video wall (with six outputs: W600, W9000, W9100)
Crossfire has a different function and has nothing to do with video walls.