I am doing a project where I need to send some numbers between arduinos. But it has to be wirelessly because they will be moving. How to Communicate between arduinos wirelessly? I need to send data between them. Wifi would be preferred.
You can use XBees. They are powerful and do provide wifi connections (the recent versions).
And you rely on well-designed devices which guarantee packet retransmission and they achieve up to 1km in an open field.
XBee still works with serial communications making them an excellent tool for your embedded project.
Just plug your Arduinos and write code to send/receive data. This library is a good start point for API mode.
If you don't mind using all the benefits from ZigBee protocol, just use AT mode where all you push in one side is sent to another via serial communication.
As has been mentioned in the comments, you have at least three possible solutions:
All of these will handle 20 feet of separation. All of these have high quality libraries for Arduinos and lots of free tutorials and assistance via forums and Stack Exchanges.
Some of the primary differences are price, size of data and power consumption.
My personal weapon of choice, and not knowing anything further about your project ... is the nRF24. This is crazy cheap and pretty easy to use. It also benefits from no need for a Wifi access point and also has a broadcast capability so that multiple devices can receive the same message. The down sides are that it is a private protocol that your phone and laptop can't decode natively (it isn't WiFi).
My second choice would be Bluetooth. This would allow your phone and laptop to be transmitters and receivers as there are plenty of great Bluetooth terminal emulators available.