Am I right to say for DFA is a unit trust whereby funds are selected by a DFA trained advisors which follows the evidence backed research? If yes, it is still actively picking equities/bonds but not rebalancing it and just invest passively?

Dimensional Fund Advisors are a fund house like Aberdeen, Blackrock, Vanguard, etc.

They founded an evidence backed investment philosophy that has shown that there are factors (dimensions) that have returned above market returns.

1) Small cap companies do better than large cap companies

2) Value does better than growth

3) Profitable companies does better than less profitable companies

Using these 3 factors for their equity portfolios, they have created funds that will buy companies that fall into this list.

One of their funds, the World Equity Fund, holds obver 10000 securities from 44 countries that passes their framework.

Only when certain stocks no longer pass their framework or when stocks come into their framework, will they make a decision to buy or sell the units.

So their funds almost work like index funds, it's just that index is created by them which is created from a theoretical or scientific look at it, and then the practical aspect is in the fund management.

Now because there aren't any more guesses to be made, they can charge very low fees like index funds.

But you have constant attention to the portfolios/funds they provide as they are looking at it every day.