There are many reasons one might have a candle-lighting ceremony, many of which are religious or spiritual in nature. One example is when a bride and groom light a unity candle during their wedding ceremony. This signifies the two people coming together as one, much as the two flames of their respective candles join to form one flame on the unity candle.
Many religious traditions also involve candle-lighting ceremonies. For instance, Jewish celebrations often involve lighting candles representing blessings for their people. In some ceremonies, both religious and non-religious, the flame of the candle may represent the light within each person.
Another popular candle-lighting ceremony is the candlelight vigil. This involves a large group of people coming together to light candles to raise awareness or garner attention for a specific person or purpose. In some cases, this may be to spread awareness about a certain disease or public issue. In this case, they are a non-violent and peaceful way to bring attention to important issues which impact the population. Other times, a candlelight vigil may be done in memory of a person or group of people. For instance, after a tragedy, such as a murder or mass act of violence, candlelight vigils are often held in memory of those lost, as well as to raise awareness for the issue of violent crimes.
Sometimes candlelight ceremonies are done as a symbol of hope. For example, if someone is missing, family members may hold a candlelight ceremony to show their hope for a safe return, as well as for raising awareness of their loved one being missing.