Vexillology, the study of flags, employs an arcane lexicon that ultimately derives from medieval heraldry (see this website for some of this vocabulary). I would describe the Hawaiian flag (just right of center in the photo above) as something like "the British flag in the top-left corner with stripes on the rest of it" but the flag is officially described in these terms:
(1) The Hawaiian flag shall consist of eight horizontal stripes, alternately white, red, blue, etc., beginning at the top, having a jack cantoned in the dexter chief angle next to the point of suspension;
(2) The jack shall consist of a blue field charged with a compound saltire (crossing) of alternate tincture white and red, the white having precedence; a narrow edge of white borders each red side of the saltire;(3) A red cross bordered with white is charged (placed) over all.
[From The Hawaii Revised Statues, Vol. 1, Ch. 5, Sec. 19 - see here]
earlier posting for a fuller description).
For more on each of the 50 state flags, see this website.