Referring to Pesaran (2015) the NW covariance matrix is computed according to the following formula:
$$\hat V(\hat\beta)=\frac{1}{T}Q_T^{-1}\hat S_TQ_T^{-1}$$
(Skipping the definition of Q)
$$\hat S_T=\hat\Omega_0+\sum_{j=1}^mw(j,m)(\hat\Omega_j+\hat\Omega_j').$$
(Skipping the definition of $\hat\Omega_j$) Where the Bartlett Kernel is
$$w(j,m)=1-\frac{j}{m+1}.$$
Could someone shed some light on what exactly the Bartlett Kernel "does" for me (and how it "works")? I seem to struggle with understanding the basic theoretical construct that underlies this.