An accelerator is like a VIP pass you buy at a busy amusement park. When mempools are congested with many unconfirmed transactions, you can pay extra to have someone with mining connections (or a specialized service) prioritize your transaction. They rebroadcast your transaction to miners or push it into special queues, aiming to get it confirmed more quickly.

Some accelerators charge a separate fee, while others might let you submit if your fee meets a certain threshold. It’s a convenience for users who can’t wait for their transaction to confirm naturally at lower fees. Of course, it’s an optional service and depends on cooperation from miners or pools running the accelerator. Still, it highlights the free-market aspect of Bitcoin: if you need speed, you can usually pay for it.