Cisgender means the person has a gender identity that matches the sex they were assigned at birth.
If you are a man and you were assigned male at birth, you are cis.
If you are a man and you were assigned female at birth, you are trans.
Non-binary can mean anything from not having a strong specifically male or female identity to closer to switching identities (bi-gender falls closer into this) to just having a lot of serious fluidity, but typically speaking at least part of the time the identity doesn’t match the assigned sex at birth.