An array (or ArrayList/dynamic array) stores elements next to each other in memory, so random access is O(1). Inserts/deletes in the middle are O(n) because elements must shift (and resizing may copy). A LinkedList stores nodes linked by pointers: inserts/deletes at a known node are O(1), but random access is O(n) and it uses extra memory.
Expanding on the short answer — what usually matters in practice:
A tiny example (an explanation template):
// Example: discuss trade-offs for "difference-between-array-and-linkedlist?"
function explain() {
// Start from the core idea:
// Arrays have fixed size and fast access (O(1)). LinkedLists have dynamic size and fast inse
}