Industry 4.0 is a new concept that has attracted the interest of many people in different disciplines. However, it remains relatively unknown as a concept by many companies, especially small and medium-sized enterprises (SMEs). The first objective of this study is therefore to illustrate the facets of the “Industry 4.0” concept from 54 definitions, in order to better understand it. The second objective is to conduct qualitative exploratory research to i) identify the perceptions of manufacturing SME managers regarding the benefits, challenges, and barriers associated with the adoption of Industry 4.0, ii) compare these findings with the results in the scientific literature, and iii) recommend a range of levers for use by SMEs to guide them in the successful implementation of Industry 4.0. Fifteen semi-structured interviews were conducted with manufacturing SMEs. First, our analyses of the 54 definitions made it possible to define Industry 4.0 by considering the three facets of “What?” “Why?” and “How?” Next, the results of the empirical study revealed the challenges (economic, technical, material, logistical, strategic, relational, and planning), benefits (increase in product production and quality, improved working conditions, decentralized and digitized production, and increased innovation capacity and data availability), and barriers (financial resources, human resources, skills, technology, and strategy). The results particularly highlighted the necessary skills (operational, technical, managerial, social, and personal) as an essential prerequisite. To implement this new environment, the article recommends a series of levers for SMEs, including, among others, establishing good change management through the development of new strategies and business models, and the adoption of a new corporate culture, with consistent leadership, planning, and implementation.