A typical Mozart-concert was with strings or piano. He played together with hist sister on the piano. He also performed concerts solo on the piano or even conducted performances sitting at the piano. He wrote string-quartettes. Strings can be transported easily and so strings are good instruments for house-music or loose engaged musicians.
A quartette (italian Quatuor) is a musical piece for four musicians, formerly singers. At Mozart's time a typical string-quartette had two violin, a viola, a chello.
Today Mozart-music is played in Musikverein, Konzerthaus (concert hall), opera and at park-concerts. Tickets for events are available at cassa or ticket-offices. Some offer internet-services to book tickets online.