Proportional representation refers to voting systems where, for whatever qualities people use to elect their representatives (whether it be ideology, ethnicity, gender, etc.), the proportion of representatives having those qualities is approximately the same as the proportion of voters having that quality.
Some election systems that strive to achieve proportional representation include single transfer voting and party-list proportional representation. Other systems, such as plurality voting, are sometimes made more proportional by gerrymandering districts to ensure that a minority group is in the majority in one ore more specific districts.
Proportional representation election systems are used to elect the parliament in Germany and many other countries.