JMeter Testing

Hi all,

     I have made a web-service in php. I had run a load test on the same by using testing tool Jmeter. And got the result in as graph, please help me to analyze the graph. It shows 3 important parameters that are 1)Deviation, 2) Median and 3) Average. Please help  to understand how those parameters affect the performance of  the web-service ?

Thanks in advance