Linear search finds the location of an item within an unordered array (collection of data). The algorithm starts at the beginning of the array and checks to see if the first item is the one that is being searched for - if not it moves onto the next item and repeats the process until it finds the desired data.
In terms of performance it can have the best case (finding the desired item first time) and worst case scenario (fining the desired item last).
The major benefit is that it can be ran on an unordered array, however the average case time may be too impractical for larger arrays
The performance limitation of linear search may not be as apparent in a small array, however will become apparent if you are searching for an item in one with millions of entries.
A binary search can only be carried out on an ordered array (numerical or alphabetical) and while more performant is significantly more complex:
The binary seach starts at the middle value, comparing that value to the on that is being searched for. If it is the correct value the search is complete, if not the algorithm determines if the value being searched for is less than or greater than the middle value. The half of the array which the value cannot be in is then discarded along with the middle value. The new middle value is compared and these steps are repeated.
Using a binary search in the example above allowed us to find our desired value in 2 iterations (repeats) of the algorithm. If we were to use a linear search it would have taken 8 iterations! However we could not have ran a binary search on a similar unordered array. Providing an array is in order a binary search will be the most efficent search algorithm available for us to use.