What is a mikveh in a Jewish synagogue?

Answer 1

A mikveh is a pool or body of water fed by mayim chayim, or "living waters", used for ritual purification of Jewish men and women. The term "living waters" refers to any naturally occurring and flowing source of water.

Answer 2

You remove your clothing, you wade into the water, you say a blessing praising God for commanding us to immerse ourselves, an then you duck under so you are fully immersed, typically three times. Frequently, you are asked to shower first, to keep the water in the mikveh clean. You may be immersing as a matter of purity. Tradition says that women should immerse after their periods end, and some men immerse before holy days. You may be immersing for the sake of conversion. In that case, there will be witnesses, typically they look in after you're mostly in the water so all they see is your head. A loose robe may be worn into the water if the mikveh is not entirely private -- a rain-fed lake or a spring-fed streams can serve as a mikveh, for example.