The concerto grosso is a form of instrumental music, popular in the Baroque period which consists of a string ensemble or orchestra' (the “ripieno” or “concerto grosso”– literally “big concerto”) which plays with and against a small number of soloists (the “concertino” – “little concerto”).
The form came to popularity with the 6 works by Arcangelo Corelli, (who may have coined the term) and was taken up by others within a short time. Handel’s 6 Opus 3, set for primarily woodwind soloists;  and the 12 Opus 6, where the concertino is scored for two violins and a cello,  are amongst the most popular baroque orchestral music played today. (The form was so popular in London at the time that Handel was forced to cobble together arrangements of music from many of his other works for his Opus 3 set to meet the demand.) J. S. Bach’s “Brandenburg Concertos” are generally in concerto grosso form. 
The form disappeared with the end of the baroque era, but came to life again during the 20th century with notable works by a number of composers.