a.shift(8) = will create a new array and store it to memory
linked list: need a node structure and connected to other elements need anohter data type to keep track
definining the relationships through one another
advantages: less expensive, each node has its own properties
- singly link list
- doesn't know the properties of the next element
- double link list
- node data structure has previos pointer and forward pointer
- can have circular data structure