ordinary people; common folk; the general public
Refers to the average person or the masses, often in contrast to elites, specialists, or the wealthy. Neutral in register.
It's a luxury item beyond the reach of ordinary people.
That policy greatly changed the lives of the common folk.
庶民 alone also means 'common people', but 一般庶民 emphasizes 'ordinary' more explicitly and is slightly more formal.
一般市民 refers to 'ordinary citizens' and is more common in legal or civic contexts, while 一般庶民 has a broader, more traditional feel.
Compound of 一般 (ippan, 'general') and 庶民 (shomin, 'common people'). The exact historical derivation is uncertain, but the combination straightforwardly means 'ordinary common people'.