Unlike the WaterFall method, Agile Testing can begin at the start of the project with continuous integration between development and testing. Agile Testing is not sequential (in the sense it's executed only after coding phase) but continuous.
An agile team works as a single team towards a common objective of achieving Quality. Agile Testing has shorter time frames called iterations (say from 1 to 4 weeks). This methodology is also called release, or delivery driven approach since it gives a better prediction on the workable products in short duration of time.