What is it?

Systems analysis is generally regarded as the breaking down of systems and processes into functional responsibility groups. Once they are all broken into groups and it is visible as to who is responsible for what, the process of rectifying any issues can begin.

As defined in www.wikipedia.com

"The terms analysis and synthesis come from classical Greek where they mean respectively "to take apart" and "to put together". These terms are used in scientific disciplines from mathematics and logic to economy and psychology to denote similar investigative procedures. In general, analysis is defined as the procedure by which we break down an intellectual or substantial whole into parts or components. Synthesis is defined as the opposite procedure: to combine separate elements or components in order to form a coherent whole."

A process of analysis has to be done before embarking on small or large scale business or web system so that pitfalls can be avoided and plans put in place for architectural issues such as performance and scalability.