Both the 190 and the 189 are permanent skilled migration visas that grant immediate permanent residence through the points test. The critical difference is nomination: the 189 (Skilled Independent) requires no nomination and is fully independent, but only allows occupations on the MLTSSL and requires a higher unaided points score. The 190 (Skilled Nominated) requires nomination from a state or territory government, which adds 5 points to your score and opens access to occupations on both the MLTSSL and STSOL.
In practice, the 190 is often the better strategic option for applicants whose occupation is only on the STSOL (not the MLTSSL), or who need those 5 extra nomination points to push their score to a competitive level. The trade-off is a 2-year commitment to live and work in the nominating state after grant.

