Beverage made of carbonated water which has been coloured, flavoured, sweetened (artificially or with sugar), with caffeine optinally added. Known as soda/soda pop/soda in North America. Many claim it is
best drunk from a glass. Common brands are Coke and Pepsi.

More generally speaking, a soft drink is a beverage that doesn't contain alcohol, or atleast not any significant amounts. The contrary to this would be (obviously) a hard drink, however, the term hard drink is somewhat archaic nowadays.