What he means is - is the company traded on an open market or exchange allowing an individual to invest in the company by buying stock or other securities.
Blohm and Voss and HDW are a listed company, under parent ThyssenKrupp, I believe they are listed on German stock exchange.
The ThyssenKrupp AG is listed in the DAX (Deutscher Aktienindex. Translation: German share index) This is the index of the 30 biggest companies in Germany. Lürssen is not listed, because they are not a Aktiengesellschaft.
Fish 14, do you want to invest in a boat co.? Try something you can keep an eye on locally, like Marinemax. They are gobbling up a lot of blue chip US boat builders and are listed on the New York Stock Exchange. Trading at around 30 bucks a share, they appear to be at one of their low spots and positioned to bounce up into the upper 30s. Good earnings & revenue, plus a P/E of 16 means it's a value relative to the SP500's typical offerings. Wonder what a Lurssen stock certificate would look like, though.