An SRR file is used to re-create a RAR file. If you are just downloading files, you can ignore SRR files. They are similar to SFV files and only contain “meta” information. That is, they only contain information about the other files that they come along with. SRRs do not contain any audio, video, or anything else in which the average downloader might be interested.
SRR files are created by a program called ReScene. The word “scene” here has nothing to do with scenes from a video production. Rather it refers to “The Scene“, which is a community of distinguished gentleman who have adopted standards for the files that they release.
So, a “release” will contain the RAR files, PAR files, an SFV file, an NZB file, an NFO file, etc. And now increasingly, an SRR file. The average downloader would use the PARs to make sure that the RARs were OK, extract the files from the RARs, and then throw away RARs, PARs, SFV, NZB, NFO, SRR, and any other ancillary files included.