It is quite complicated in MS SQL SERVER.

-- Use a Common Table Expression (CTE) to create a temporary table 
-- which is only valid for this query to join tables. 
WITH cte AS (
select a.Artikel, a.Name, lb.Menge, 
lb.Platz 
from Artikel a 
JOIN LAGERBELEGUNG lb on a.ARTIKEL = lb.Artikel 
where a.SACHGRUPPENKLASSE like 'Ven%' and a.Name like '%2016%') 

-- Use a query with STUFF and FOR XML PATH on the CTE for concatenation

select t.Artikel, max(t.Name) Name
     , stuff( ( select ', ' + Platz
                from cte
                where Artikel = t.Artikel
                for xml path('') ), 1, 1, '') AS Platz
from cte t
group by t.Artikel

More about FOR XML PATH and STUFF on Stackoverflow, see 1st and 2nd post there.
And more on Sqlshack.