These are all averages. say you have O(n) seach time, but it takes just one. Its average time not realistic time.
O(n) - Searching Unsorted
Iterate through all the items and manually check. is it the 1st one? no. is it the 2st one? no. is it the 3rd one? no. is it the 4st one? yes. linear time
O(log n) - Binary Trees - Searching sorted
First sorts the list from smallest to largest. starts at middle, splits is the number is larger or smaller,
Bogo sort - Unstored - O(n^2)
You pick a random position and check if its the same as your value. if you stored this random position if its false, then you have a linear time.