SQR (Structured Query Reporter) Question:

Load Lookup is essentailly an array which acts in the form of a table. Load Lookup is used to reduce the complexity of joins - it populates the values of a certain field depending on the ke field specified from a certain table. Then the users can query from the preloaded lookup table instead of joining tables.

While arrays are used to store and retrieve data using the get and put commands

Apart from above mentioned advantages,Load Lookup increases the performance as it loads an array into memory with key and return value.