The significance at the time is as Blank said, that the 93rd Highlanders held off the Russian cavalry charge in line, rather than in square. Standard tactics of the period held that meeting a cavalry charge in line was a recipe for disaster, but in this case, it worked, due to excellent tactical command, the traditional steadfastness and discipline of the British infantry under fire, and the high weight of fire the British were able to put out.
The battle of Balaclava is full of the British doing things that were normally considered to be tactically disaterous (and for good reason) and getting away with it (mostly).
The famous Charge of the Light Brigade broke the rule that cavalry don’t charge artillery (especially down at the end of a long valley with more artillery lined up on both sides as well). The charge was actually a sucess in that they did reach the artillery batteries at the end and kill or drive off the gunners, but the regiments involved suffered very high casualties.
The lesser-known Charge of the Heavy Brigade saw the British heavy cavalry carry out a sucessful charge uphill and through the British camp lines against Russian cavalry, both conditions normally disasterous for a cavalry charge, as the cavalry would arrive disordered and without the momentum normally required to break the cohesion of the enemy.