Workers' self-management is the management of a productive enterprise by the workers of that enterprise themselves. It is distinct from management by a capitalist or by capitalist-appointed managers, and from management by state-appointed managers. It is debateable whether workers' self-management is socialism, because the worker self-managed enterprise is still in market relations with other enterprises from which it buys its materials, and with other enterprises or the public to whom it sells its product. However, neither is worker self-management capitalism, because the enterprise is not owned by a capitalist, and there is no appropriation of surplus value from the workers.
From Harry Braverman, Labor and Monopoly Capital:
Without the return of requisite technical knowlege to the mass of workers and the reshaping of the organization of labor – without, in a word, a new and truly collective mode of production – balloting within factories and offices does not alter the fact that the workers remain as dependent as before on "experts", and can only choose among them, or vote for alternatives presented by them. Thus genuine worker's control has as its prerequisite the demystifying of technology and the reorganization of the mode of production." (P 445.)