Hey there!
An expression doesn't have a left side, right side, or even an equals sign. It could just be something like "2+3" that you would just need to simplify.
However,
An equation sets two expressions/terms equal to each other, has a right and left side, and has an equal sign.
Finally, an inequality " a relation that holds between two values when they are different." They use greater than, less than, greater than or equal to, or less than or equal to signs.
Hope this helps!