What is the definition of gluLookAt?

The description of the gluLookAt is as follows:

Let

F=centerX-eyeXcenterY-eyeYcenterZ-eyeZ

Let UP be the vector upXupYupZ.

Then normalize as follows:

f=FF

UP″=UPUP

Finally, let s=f×UP″, and u=s×f.

M is then constructed as follows:

M=s0s1s20u0u1u20-f0-f1-f200001 //??????

gluLookAt is equivalent to

glMultMatrixf(M);

glTranslated(-eyex, -eyey, -eyez);

Can you explain the description above?Especially the define of M,the line with ????.

Thank you very much.