difference between DPC and DPM?

DPC is a linear strip, typically fitted at the base of walls to break the path of moisture otherwise heading upwards from fountations into the wall, while a DPM is a wider membrane and comes in large sheets or rolls, and typically does a similar job resisting moisture penetration from under a whole foundation floor slab. Generally not to be relied on exclusivily - there should always be secondary lines of defense to mitigate against moisture ingress