Cross correlation peak value
It's the correlation coefficient that you get for maximum matching, which is the squared Euclidean 2 norm of the signal $s(t)$, ie. $||s||_2^2$; when you note down the crosscorrelation in terms of integrals, you'll quickly notice that, if you use both signals for correlation, the value for $\tau=0$ is the same as the energy in the signal.