In Linear Structures such as Array, queue, etc, -> Simple searches like Linear Search & Binary Search are used

In Non-Linear Structures such as Graphs Trees, etc, -> Recursive Searches such as BFS, DFS or other methods are used

In large collection of text objects, search can be done not on basis of index, going one by one, but with O(1) via indexing, such as Inverted Index, used in Elastic Search & Search Gngines