Bribery is when one party unethically offers another party something of value in exchange for favorable treatment. People who are bribed are usually people who hold positions of interest relative to the bribing party. For example, a person who owns a construction company may try to bribe a governmental official with a sum of money in order to get a building permit when they may not otherwise get it.
Bribery is used when one party wishes to sway another party into doing something they wouldn't otherwise do. Bribery is a crime. Both the giving and receiving party can be held accountable. People typically attempt to use bribery when they want to do something that is illegal or unethical. If the activity was not illegal or unethical, then the two parties could just exchange value normally. For example, one party could offer to pay another party to mow their lawn. However, if one party desires to have another party rig the results of an election, they may attempt to use bribery. This would be illegal.