Bursting: All EFS file systems, regardless of size, can burst up to 100 MiB/s of metered throughput, if they have burst credits.

Provisioned: you will pay additional cost for any bursting

Use Bursting Throughput mode if your workloads are typically spiky. A spiky workload drives high levels of throughput for short periods of time, with otherwise low levels of throughput. For applications that have a relatively constant throughput, use Provisioned mode.