Flute” is the term (in English) for a transverse instrument (held sideways) that you blow across. Modern band and orchestra flutes are usually metal and have keys with a separate head joint, but that is a subset of the “flute” category. read more
The difference is in the range and number of holes. A flute has a specific number of holes (usually with keys. except for older flutes) to allow for chromatic playing, and a specific length and width. The flute's standards have long been set by orchestral players, and the same can be said of the piccolo. read more