هَلْ and أ are interrogative particles (أدَواتُ الإسْتِفْهامِ). They are used in questions:
؟ أ هَذا أخوكَ Is this your brother?
أ سافَرَ عَلي ؟ Did Ali travel [depart]?
هَلْ أنْتِ مُسْتَعَدَّةٌ ؟ Are you (feminine) ready?
هَلْ تُحِبُّ عَمَلَكَ ؟ Do you like your job?
See also: