Oversimplifiying, they are chargeless electrons.

If you have an electron(negative) and a proton (positive), then the charge may jump and you get a neutrino(no charge) and a neutron(no charge).

It's more common in the other direction. If ypu have a neutron(no charge) it splits into a proton(positive), an electron(negative) an an antineutrino(no charge).