TVETipedia

It is most prevalent in informal sector enterprises but could also exist in formal sector enterprises where employment relations continue to be informal and earlier apprenticeship practices are continued. (…) Compared to quality apprenticeship, informal apprenticeship falls short of important criteria: usually there is no off-the-job learning, no recognized qualification, contracts are mostly oral, and rules are informal.

Informal apprenticeship refers to the system by which a young learner (the apprentice) acquires the skills for a trade or craft in a micro- or small enterprise learning and working side by side with an experienced craftsperson. Apprentice and master craftsperson conclude a training agreement that is embedded in local norms and traditions of a society. Costs of training are shared between apprentice and master craftsperson.