It’s a series of attacks that you repeat, with or without a definite end… if the loop doesn’t have a definite end, or can go on for a very, very long time, it’s sometimes called an “infinite,” like MvC2 Ironman’s [j.LP, MP, MK, U+H] - though technically, under normal circumstances, this infinite will end when the character “dizzies out” after awhile.
Think of El Fuerte’s last trial in SSFIV, where you have to connect three HPs in a row. People call the method for executing that combo “Run, Stop, Fierce” or RSF. You’re "loop"ing [HP xx Habanero Dash, Sudden Stop]. in the case of the RSF, it will eventually end since the dummy character gets pushed back with each repetition.
hope that helps.