What do these icons mean?

[BB Shockwave]

Broken arrow means the archer will only inflict half the damage on that enemy as it is out of range. You need to move the archer closer - or wait for the enemy to come nearer - in order to inflict full damage. Keep in mind though, this doesn't have to be half the size of the arena - for some units their full range is in 5 hexes, for others, more or less. Some, like the Cyclops or the Archmage, can shoot for full damage anywhere.