A SD memory card is a small chip designed to provide storage to portable devices. Light and extremely small in the case of a MicroSD, all the cards come in a variety of speeds.
In the above image on the left is a SanDisk Extreme SDHC card. The 10 inside a circle is the speed class, 10 is the quickest made for full HD recordings. 2 is the slowest with 4 and 6 being suitable to record HD. The 3 inside the U is the Ultra high speed class (UHS) there are two classes: 1 and 3. If you have a 10 for speed class and 3 for ultra high speed class your card is very quick and can do ultra HD recordings or 4k!
You will also note the SDHC card having 90MB/s on it, card manufacturers usually only highlight the read speed as this is the quickest. Read speed is the speed when reading or moving data from the card. The write speed is what determines how quickly your card can capture and save. A slow write speed means your footage can be choppy and laggy.
32, 64, 128 and 256 Gigabytes are the common storage sizes cards come in now days, Smart file management means you should be doing a backup to your PC and then wiping your card after each outing. Hence 32GB is fine for a card size as a beginner.
MicroSD for multi use
Cameras are the long-standing users of the larger SDHC cards whilst drones, action cameras, phones and Nintendo switches use the smaller MicroSD card. It’s always handy to have an adapter if you use Cameras and a drone to easily switch your expensive high-speed MicroSD card between devices.