In the Proximal Convoluted Tubule there is selective re-absorption of water and salt, depending on how dehydrated the body is.
In the presence of ADH, much more water is reabsorbed than when ADH isn't present.
Microvilli also helps to expand surface area to allow for more absorption.
Filtration, on the other hand, is not selective at all as it is important that essential nutrients return to the body so sugar, vitamins, and other organic nutrients are reabsorbed into the filtrate.
Some are actively transported (glucose, amino acids, Na+) and some are passively transported (H2O, K+, Cl-).