y = logspace(a,b,n) generates n points between decades 10^a and 10^b.
rng('default') puts the settings of the random number generator used by rand, randi, and randn to their default values so that they produce the same random numbers as if you restarted MATLAB. The default settings are the Mersenne Twister with seed 0.
Well, you get the idea. If, after reading the documentation, you still have some questions, feel free to ask again.
MATLAB mathematical toolbox documentation