OR{ }Keeps messages that match at least one of the criteria.
Join two criteria with OR to get the messages that match one, the other, or both. Curly braces do the same in shorter form: everything inside { } is treated as an alternative.
from:amy OR from:davidOpen in Gmail ↗Messages from either person.
{from:amy from:david}Open in Gmail ↗Same result with braces.
has:yellow-star OR has:purple-questionOpen in Gmail ↗Messages carrying either of these icons.
OR when you have many alternatives.from: as well as with has:.Google documents no limits for this operator.