FFT for Spectral Analysis

Question

Can someone explain me these lines of python code, and the role of each line ?

thank you in advance.

X_f = abs(sf.fft(x))
l = np.size(x)
fr = (Fs/2)*np.linspace(0.1, l/2)
xl_m = (2/l)*abs(X_f[0:np.size(fr)]);