and

Description

and sets as a condition that both expressions have to be true, for the entire expression to evaluate to true.

Unknown values

and follows three-valued logic. Because a single false is enough to make the whole expression false, false and unknown is false, not unknown - the unknown side cannot change a false and, so the rule resolves to a definite false rather than staying pending. The expression only becomes unknown when the missing side could still flip the outcome (for example true and unknown).

and	true	false	unknown
true	true	false	unknown
false	false	false	false
unknown	unknown	false	unknown

Need the second question to be asked only after the first is answered? Use and then instead.

Example

If a bank only offers certain services to people who are a citizen of an EU member state, and also pay taxes in the European Union, this is how to check against both those requirements:

p is Person
p.nationality contains any EUCountries 
and
p.tax_domicile in EUCountries