Serialization which help us to store or transport PHP data structure such as an array or object. All the storage meduim or database can store String type. It will generates a storable representation of a value. This is useful for storing or passing PHP values around without losing their type and structure.
Essentially, it takes a php array or object and converts it to a string (which you can then transmit or store as you see fit).
i.e, serialize() allows you to store one of these structs as a string. It can be de-serialised from its string representation with unserialize().
If you are familiar with json_encode() and json_decode() both the concept is similar.
Using Serialize method, We can store multiple field key & its values in single column. You can easily extend your forms without changing table structure.