Full Siblings:
Two people having both biological parents in common

Half Siblings:
Two people having only one biological parent in common

Step Siblings:
Two people having no biological parents in common but one of each of their biological parents marry each other.

Entering Step or Half on the Calculator
There is no way to enter a half relationship on this calculator, so it will never report a half result.
To enter step relationships on the calculator, type parent's-spouse's child instead of parent's-child.
It will report a non-blood result, which implies the step relationship.