The basic idea is that if we take a lot of the money that currently goes to the police in order to catch people who have committed crimes, and instead invest that money into education, into healthcare, into social services, we can help prevent crimes from happening in the first place. Likewise, we have police doing a lot of jobs that might better be suited for social workers or medical professionals, and giving those groups more money so they can deal with those problems instead, so that police can focus on what they're best suited for, is also seen as a better idea.

Instead of having a police officer deal with a homeless person with a drug addiction, a counselor or social worker with specific training for this situation would do the job better.

Basically, if we try to prevent crime from happening in the first place by addressing the issues that lead to it, we won't need as many police in the first place, and we'll have less police brutality as a result.