L2 norm is $$ L{2}=\sqrt {\sum{1}^{i} (x_i^2)} $$
For example, if x = (1,-1,2) the L2 norm of x is $$\sqrt{(1+1+4)} = \sqrt{6} $$
By dividing x’s each element from L2 we normalise x into unit L2
$$ \frac{x{i}}{L{2}}, \forall x $$
For example after normalisation, $$ x=(\frac{1}{\sqrt{6}},\frac{-1}{\sqrt{6}}, \frac{2}{\sqrt{6}}) $$