Visma is a group that owns and develops business software companies. Its member companies provide cloud software for accounting, ERP, payroll, invoicing and HR, among other things, mainly for smaller businesses and public-sector organisations. Visma lets each acquired company operate close to its customers, in their language and under their local laws, so the offering differs by country and product. The software is typically consumed as SaaS; some products also run on the customer's own infrastructure.
Visma is headquartered in Oslo, Norway, which is inside the EEA but outside the EU. According to Wikipedia, a majority of the shares is held by the investor HgCapital, alongside other institutional investors. Where data is hosted depends on the product and customer; the Visma Trust Center brings together security and privacy information and points to product-specific documentation. For a European organisation it is worth checking hosting location, subprocessors and the ownership structure for each product, because the group consists of many separate companies.