When you are new at eCatt, a brief overall description can be useful. Catt stands for Computer Aided Test Tool is the tool to automate test scripts in SAP. In effect, a sequence of system-processing steps are recorded and can be executed at a later stage to test the effect of a development or customizing change.
The e in eCatt stands for "Extended", ergo: the more adult version of Catt. If you are dealing with a serious project and you want to ensure the knowledge required for testing is not required till the year 2050, working with computer aided test tools is a winner-formulea.