SRS is a complete description of the behavior of a system to be developed. It includes a set of use cases that describe all the interactions the users will have with the software. Use cases are also known as functional requirements. In addition to use cases, the SRS also contains non-functional (or supplementary) requirements. Non-functional requirements are requirements which impose constraints on the design or implementation (such as performance engineering requirements, quality standards, or design constraints).
I find the following srs formats to be really useful while preparing design document for my final year project.
www.processimpact.com/process_assets/srs_template.doc
www.cc.gatech.edu/classes/AY2003/cs3911_summer/srs.doc
