Dependent and independent KCL equations
If you have a network with n nodes, there will be \$n-1\$ independent KCL equations. 

That means the KCL equations alone are not sufficient to produce a unique solution to the circuit. One more equation is required to produce a solvable set of equations.

Normally, the one additional equation is produced by designating one of the nodes as the "ground" node, and arbitrarily choosing that its potential will be considered as 0 V.