A hashmap uses a hashtable, however, it is internally implemented using two data structures namely an array and a linked list. Whenever you declare a hashmap, internally, it will create an array of buckets. The buckets are referred to as nodes or you can say a linked list.
Hash function in dictionary will take value and give index of array where the value should be stored.
Example
HashFunc(param) {
If (param == ‘a’) return 26;
}