The object of the game is essentially a very simple one. It’s played on a usually square area of closely mown grass called ‘the green’, which is divided into strips or playing areas known as ‘rinks’. The green is surrounded by a small ditch to catch bowls which leave the green and a ‘bank’ where markers are placed to indicate the corners and centrelines of each rink.
Players take turns to roll or ‘deliver’ their bowls from a mat at one end of the rink towards a small yellow or white ball, called ‘the jack’ at the other end. All bowls are shaped with a bias so that they take a curved path towards the jack. To be successful the bowl must be delivered with the correct weight, along the correct line.
The object of the game is to get one or more of your bowls closer to the jack than your opponents on each end. You or your team scores one point for each bowl that ends up closer than your opponents after all bowls have been delivered.
There are many different formats of the game but the most common are singles or teams of pairs, triples or fours. In singles, the winner is the first to score 21 points. In the other three formats, the winner is the team that scores the most points over a set number of ends.
For a more comprehensive article helping to explain the basics see here