Job Evaluation 101
Job Ranking is the most simple form. Basically you just order the jobs according to perceived seniority. It's easy in a small organisation, but get exponentially difficult with lots of different jobs.
Pair Comparison introduces more rigour by comparing jobs in pairs, but really it's a more structured way of building a basic rank order.
Benchmarking or slotting sets up certain jobs that are analysed in detail. These are then used for comparison to slot jobs against these benchmarks.
Job Matching allocates benchmarks too, but when a position is matched the elements of the job that differ are re-evaluated.