後進

less advanced / underdeveloped / lagging behind / the younger generation / the less experienced ones

back / behind / rear / afterwards / after / later / post-

to go forward / to advance / to go in / to enter / to put in / to submit / to take in / to admit / (math.) base of a number system / classifier for sections in a building or residential compound

to come late and leave first / last in, first out (LIFO)