A special slot for inserting a memory card. Memory cards allow you to expand the phone's built-in memory (or in the past these slots have been used to add some missing features such as Wi-Fi connectivity).
Memory cards have different capacities and are used to store and transfer files between compatible devices. There are several types of memory cards. The most popular and frequently used by mobile phone manufacturers is microSD; however, up until recently Sony Ericsson exclusively used the Memory Stick Micro (M2) card type developed by Sony.
Memory card slots can have various supported memory card capacities. Depending on the device, card slots can support capacities of up to 512GB or even the yet unavailable 2TB.>
As manufacturers rarely test their products for compatibility with newer and larger cards that come out after a specific handset is out on the market, whenever it is possible, we try to verify that larger capacity cards run on older phones.
When we confirm that a mobile phone works with a larger capacity memory card than what the manufacturer has advertized, we usually put that down in the phone specs sheet in our database.
That way, when you see the word "verified" in the Card slot field, you will know our reviewing team has personally tested the device for compatibility with the stated capacity and they are compatible even though it may not be officially stated so by the manufacturer.
Still, you should take that information with a pinch of salt, as your mileage with your specific unit may vary.