Effective means – that something turns out the way we hoped and planned.
When Christians pray and ask God for something, they really hope he will do what they have asked. Christians hope their prayers will be effective.
The Bible teaches that the prayer of a righteous person is effective. Another way of saying this is ‘the prayers of somebody who is learning and growing to be like Jesus, will be answered in the way they hoped’. Christians believe that’s not because God only wants to do things for people that live his way; but because people who are learning and growing to be more like Jesus, will be spending time with him as they read their Bibles, pray and worship. Christians believe people who spend time with Jesus start to love the same things Jesus loves and want the same things he wants.
Christians believe God gives people who spend time with Jesus what they ask for because they want the same things Jesus wants and therefore ask for the things God longs to give.
Some of the wording in this post is repeated in ‘How Can Christians Be Sure They Are Asking God For The Things He Wants To Give Them?’