Please explain each part of the pseudo code

Input: W$,$ Wi$,$ vi$,$ N

$W^r=W,v^{TT}=0,x_i=0$

${}^{\text{'}}$ is the remaing volume

$V^{TT}$ is the total value

$x_i$ is the item selection decision

calculate $r_i=\frac{v_i}{w_i}$ values for all items

sort ris vulues in non$-$iwcreasing order.

let I be the sorted item indices

for ;inI

if $w^r{w}_i$

$x_i=1$

$w^r=w^r-w_i$

$v^T=v^T+v_i$

else if $w^r>0$

$x_i=\frac{w^r}{w_i}$

$w_r=0$

$v^{TT}=v^{TT}+x_i*v_i$

utput: $x_{i}in[0,1],vT$