The .RData file format is a native binary file format used by the statistical programming language R to save and load R objects directly to and from the disk. When a user saves their current R workspace using the 'save()' function, all the variables, data frames, functions, and other objects currently loaded in memory are serialized and stored in an .RData file. This allows users to resume their work exactly where they left off without needing to reload and reprocess all the data and code. These files are highly specific to the R environment and are optimized for efficient storage and retrieval of complex R data structures. They are not intended for direct use by non-R applications, as the internal structure is proprietary to R and depends on the specific version of R used to create them. While they are binary, they are generally not compressed unless explicitly saved that way, and they often contain metadata necessary for R to correctly reconstruct the objects, including class information and attributes.