In 2012, candidates needed either one percent or 500 signatures (whichever was lower) from Democrats in each of the state's 50-plus congressional districts. They had two months to do so -- which, particularly if you're hoping to keep expenses under $5,000, is a time crunch. Other states work similarly; some don't.
A contemporary definition of rank-and-file is prevalent in labor union vernacular when referring to general membership and not union leaders. Rank-and-file generally means the employee doesn't occupy a high-level position within the organization.
File - an individual file; provides readonly information such as name, file size, mimetype, and a reference to the file handle. FileList - an array-like sequence of File objects. (Think <input type=file multiple> or dragging a directory of files from the desktop). Blob - Allows for slicing a file into byte ranges.