What is an M.2 slot on a motherboard used for?
To connect an M.2 specified SSD, your motherboard will need to have an M.2 slot.
How Qt Signals and Slots Work
The first thing Qt does when doing a connection is to find out the index of the signal and the slot. Qt will look up in the string tables of the meta object to find the corresponding indexes.
C++ Qt Signals and Slots
Most Qt widgets have slots available, to which you can connect any signal that emits the same type that it accepts. The widget documentation has the slots for each widget listed under "Public Slots".