Doing some research about SD card adapters, I found these boards with a chip on them.
They are actually very common. They have a linear voltage regulator because UNO for example use 5V but SD card adapters use 3.3V. The voltage regulator has two capacitors one on the input one on the output. but what is C3? Looks like it is between the output and GND.
The other question is what is the other chip? I guess it turns sd card signals from 3.3 to 5v and viceversa. What is the name of this and what could be this chip model?