A "symbol" is one thing that represents something else. For example, a wedding ring is a symbol for a couple's marriage.
"Symbolize" is a verb that means to be a symbol. Here's an example:
This wedding ring symbolizes our love and commitment to each other.
People think that the events that happen in your dreams are symbols for emotions or memories in your real life. People often try to interpret each other's dreams, which means to explain what the dreams mean.
There are also a lot of symbols in things like: