The AND operation will return results that satisfy all of the defined rules within your segment. This operation tends to produce a smaller result set since it’s more restrictive.
The OR operation will return results that satisfy any of the defined rules within your segment. This operation tends to produce a larger result set since it’s less restrictive.
The EXCLUDE operation will return results of the first rule, except those that you specify in the second rule. For that reason, exclude requires exactly two rules to be constructed. It will take the results of Rule 2 subtract them from the results of Rule 1 to produce your final target audience. This operation is very useful for suppressing campaign recipients or lists members to make sure they are not added to the new mailing list.