MicroSD cards: MicroSD cards are the smallest ( 15 x 11 x 1 mm) SD cards commonly used in smartphones and portable devices. MicroSD card capacity usually ranges from 64MB to 2GB . Due to this low storage capacity, the use of microSD cards is decreasing as the use of smartphones increases. One thing to note here is that many of us mistakenly refer to SD cards with a capacity of 4GB or more as MicroSD cards. But SD cards with a capacity of 4GB or more are not microSD but microSDHC or SDHC cards. SDHC Card: HC of SDHC card means High Capacity. SDHC cards allow you to store larger data or files than microSD cards. SDHC cards usually have a data storage capacity of 4 GB to 64 GB . Currently the most widely used SD card format is microSDHC . This is because an SD card with a capacity of 2GB or less is not enough to store data on current smartphones . SDXC Card: The XC of SDXC Card stands for Extended Capacity. SDXC cards allow you to store larger data or files than SDHC cards . SDXC card data storage capacity is usually 64 GB to 2 TB or 2000 GB . SD Card Speed: A number is usually given on top of microSD and SDHC cards. As we can see 10 above the card shown in the picture above . This number indicates the speed class or data transfer speed of the card. In this case class 10 means data transfer speed is 10MB per second. These numbers are usually 2-10 different even numbers. For smartphones, it is usually best to use a class 6 SD card. Class 2 for normal video recording Class 4 and 6 for high-definition video (HD) to Full HD video recording, Class 10 for Full HD video recording and consecutive recording of HD stills UHS Speed Grade 1 for real-time broadcasts and large HD video files UHS Speed Grade 3 for 4K video files SD_class_table How to use SD card: Many people know how to use SD card. Wait until the show. However, it is always best to turn off the device before opening or inserting the SD card. I have nothing to say about how many GB SD card to buy , because it depends entirely on your needs. And as I said before about the class , it is better to use class 6 card , it is better to use more class SD card. The last word is the SD card brand. In my opinion it is better to buy SD card from SanDisk, Kingston or PNY . But it is best if you use Sandisk .