Some applications model data within database systems, in which case the database system handles the details of choosing data structures, as well as the algorithms to manage them. However, in many ...

You use time complexity and space complexity functions to compare the algorithm to others of a similar nature (one sorting algorithm to another sorting algorithm, for example).

Learn when and how to use different data structures and their algorithms in your own code. This is harder as a student, as the problem assignments you'll work through just won't impart this knowledge.