The three main types of file organizers are sequential, direct and indexed.
Sequential organization means the data is written, stored and read in order so the first thing entered is at the front and each subsequent file is stored in order. Sequential organization means that not only must the records be updated in order, but accessed in order as well. This means writing and retrieving data is slower. The record is also a fixed size so it can only be changed or updated as long as the size remains the same.
Direct organization is more similar to how hard drives store data. An index is created and updated as records are added, removed or changed. Records can be entered in any order and accessed in any order using the index. This does mean an index has to be created and maintained so writing will typically be slower than reading. Also, if the index is lost or destroyed there would be some significant difficulty accessing records.
Indexed organization requires a lookup index in a separate file that manages record keys sequentially and uses pointers to locate the data. This method typically is more effective for databases as record keys and data pointers can be used to point at other record keys with the data sorted differently providing significant flexibility.