what does this lines mean?

repo = '/media/data/images/';
filelist = dir([repo '*.jpg']);
sift_descr = {}

Answer 1

[Walter Roberson]

filelist will become a struct vector, in which every entry describes a '.jpg' file found in /media/data/images/ . filelist will not be the list of files: it will information about the files. The names are in the .name field of the struct,

filenames = {filelist.name};

Note that the filenames extracted this way will not contain the directory information.

After that is done, the variable sift_descr is initialized to become an empty cell array. This step does not depend upon the previous two lines.