Institutional racism is driven, either intentionally or unintentionally, through housing, education, criminal judgement system, media, and employment.
Institutional racism is racism which regardless of racist intent, accrues in institutional laws, customs, or practices.
Institutional racism is the idea that regardless of what white people may feel on an individual level, the state of their institutions, be it the church, the union, the real estate lobby, the board of education), exclude blacks.
Institutional racism is not a useful concept, as evidenced by that fact that just because an institution has racism in it, it does not follow that there is institutional racism.
Institutional racism is a magic word which says you don't have to find anyone guilty of racism there just racist by virtue of being a of a particular race which of course is a racist statement.
Institutional racism is not a useful concept because, owing to its vagueness and lack of anything but anecdotal evidence, there is no way for society to fight it.
Institutional racism is a vicious cycle whereby housing disparity leads to low taxes which leads to poor schooling which leads to low education and dropouts and blacks entering the criminal justice system and because of the median prejudice they receive longer sentences and can't get jobs when they're finally released which leads to poor communities which leads to housing disparities, rinse, wash, and repeat.