The start of the 2004 baseball season was shrouded in a cloak of accusations of steroid use directed against various ball players, but specifically Barry Bonds. He is has hit a lot of home runs, many of them spectacularly landing outside Bonds' home stadium in San Francisco in a bay. Anyone who watches the sports part of a news broadcast will be familiar with the sights of people in rowboats waiting for a Bonds treasure.
Of course, all home runs are exciting. From the one that barely drifts over the fence (will it go over? will the outfielder make a running jump and record an out?) to the one which is a homer off the bat and flies into the upper deck. More home runs equal more people coming to the park, looking for the home run excitement. More home runs equals more score, thus a better chance of winning. More people in the park plus more score equals bigger paycheck.
So it's only natural for ball players to want an edge to succeed. It happens in poker or golf or track and field. People enthusiastic about their sport want to get ahead. Avid golfers will purchase expensive clubs that promise four hundred yard tees. It was a couple of years ago that a major golfer was found with a golf club with a head that was banned by the PGA for giving an unfair advantage. There are card sharks who mark their poker deck to know what the other players have.
Two of the most publicized was baseball players cheat is steroid taking and bat corking. Last year Sammy Sosa was shamed by having a bat break on a swing and the umpire crew finding cork inside. He claimed it was a practice bat that accidentally got used during a real game. Steroids are harder to prove. You can try to interpret signs from the player, but actual testing isn't allowed at the point without consent from the player.
What does corking a wooden bat do? The cork is not as heavy as wood, so the bat become lighter to swing with the cork core. Some people say it gives an additional "spring" to jolt the ball out.
Steroids, on the other hand, build muscle which players want to drive the ball farther. You can't just take steroids on their own. They have to be accompanied by exercise and working out. While working out alone builds muscle, the steroids are a more dramatic way, adding mass quicker and bigger.