What does it mean when appears a no Sim/SD Card when I turn on internet I got a Lollipop 5017 A, and sometimes when I use the phone internet it appears a little ícon close to the internet one that shows a card with a diagonal risk as if the phone can't find the SD/SIM card (one of the two, I'm not sure which).

When I go to Settings > Storage the option to activate SD card is grey and I can't click it.
My question is: is this SD card (the one mentioned in the Settings) a external one (the black one that we can plug in PC) or is it a reference for the SIM card, like in the folder /storage/sdcard0 ?
It would help if you shared a screenshot of the same. But I'll try to answer your question,


The SD card mentioned in the Settings is mostly external
The icon that appears close to the internet icon is usually a sim
card icon
The option to activate your SD card might appear grey if the SD card is not detected(if you have one) or not available.