Affect means to have an influence on or cause a change in. For example, “Intense lobbying affected the vote.”
Affect and effect are often used interchangeably. Affect is a verb. Effect, meaning result, “When the witness appeared on the last day of the trial, the effect was that judge granted a continuance.”; the power to produce an outcome, influence, “The government’s actions had an immediate effect on counterfeiting.”; or the condition of being in full force, is usually used as a noun, “The regulation goes into effect next year.”
However, effect can also be used as a verb meaning to bring about, create or execute. “The newly merged company tried to effect a change in the group’s hiring practices.”
When you affect a situation, you have an effect on it.
As a verb, affect most commonly means to influence: “How drinking affects health”. Effect means to bring about or execute: “The divestments are designed to effect savings.” Thus the sentence, “These measures may affect savings.” could imply that the measures may reduce savings that have already been realized, whereas, “These measures may effect savings.” implies that the measures will cause new savings to come about.
in effect: in essence; to all purposes. “Testimony that in effect contradicted her earlier statement.”