SD memory card manufacturers created “maximum” or “burst” speed designations to support consecutive picture-taking in burst shooting modes on your camera. Higher maximum speeds, which indicate read/write speeds in megabytes per second, allow photographers to take more consecutive pictures in burst mode than lower maximum speeds allow. Higher maximum speeds also enable faster data transfer to your computer.
Maximum speed is not defined by SD standards. Manufacturers indicate maximum speeds as well as capacity, Speed Classes and Bus Speeds on the SD memory card and/or the SD memory card packaging.
For more details on your camera or SD memory card, consult your user manual or the manufacturer.