What was the aim of vietnamization?

The aim of Vietnamization was to reduce American involvement in the Vietnam War by transferring all military responsibilities to South Vietnam.

It was a policy introduced by the Richard Nixon administration in an attempt to end U.S. involvement in the Vietnam War through a program to expand, equip, and train South Vietnamese forces and assign to them an ever-growing combat role, as well as reducing the number of U.S. combat troops.  

Vietnamization was Nixon's plan to train and arm the South Vietnamese so that the US could pull troops out of Vietnam it started in late 1969 and ended in 1973.