If you want to become a better chess player it is very important to have a good handling of the pieces. So, for example the rook needs open files and is happy when he can penetrate into opponent`s position and keep his position.
In the first example Black has no problem sacrificing a pawn for quick development. At the end his rook is on d2. Although it is an endgame position and Black is a pawn down, the advantage is on his side.
In the second example later world champion Botvinnik demonstrated perfect piece play. His rook on the seventh row became a decisive factor