In Saṅgītisutta three types of persons in the world are mentioned: sekkha (learner), asekkha (adept) and nevasekkha nāsekkha (ordinary person or puthujjana)
Tayo puggalā—sekkho puggalo, asekkho puggalo,
nevasekkho nāsekkho puggalo
Three kinds of persons, to wit, the learner, the adept, he
who is neither.
A sekha is someone who trains himself in higher virtues, training the mind to a higher degree and training for higher wisdom or basically someone who's training himself in the eightfold path. There are 7 types of sekhas (1) the path to stream-entry; (2) the fruition of stream-entry;
(3) the path to once-returning; (4) the fruition of once-returning;
(5) the path to non-returning; (6) the fruition of non-returning;
(7) the path to arahantship
Sekho, sekho’ti, bhante, vuccati. Kittāvatā nu kho, bhante, sekho
hotī”ti? “Sikkhatīti kho, bhikkhu, tasmā sekhoti vuccati.
Kiñca sikkhati? Adhisīlampi sikkhati, adhicittampi sikkhati,
adhipaññampi sikkhati. Sikkhatīti kho, bhikkhu, tasmā sekhoti
Venerable sir, it is said a trainee. How is one a trainee?
Bhikkhu, one trains, therefore he is called a trainee.
In what does he train? He trains in higher virtues,
training the mind to a higher degree and training for higher wisdom.
An asekha is someone who's gone beyond the training or basically an arahant.
Asekho asekho’ti, bhante, vuccati. Kittāvatā bhante, bhikkhu asekho hotī”ti? “Idha, bhikkhu, bhikkhu asekhāya sammādiṭṭhiyā samannāgato hoti, asekhena sammāsaṅkappena samannāgato hoti, ... Evaṃ kho, bhikkhu, bhikkhu asekho hotī”ti
Venerable sir, it is said, `gone beyond the training' How is the bhikkhu gone beyond the training?
Here, bhikkhus, the bhikkhu is endowed with perfect right view,
perfect right thoughts, perfect right speech, perfect right activity,
perfect right livelihood, perfect right endeavour, perfect right
mindfulness, perfect right concentration perfect right knowledge and
perfect right release gone beyond the training. Such a one is gone
beyond the training.