So I recently bought a stratocaster and an amp.

DI box

A DI box is a device that turns high-impedance instrument level to a low-impedance microphone level. The signal during the process is also balanced.

A practical setting would be connecting the guitar/bass to the microphone input. The advantages?

• you can clone the signal to another output that’s not being affected by the amplifier. This pure signal from the instrument can later on be processed through, say, an emulated amplifier of your choice. This gives your the flexibility to craft your sound. You get this clone through the quarter-inch through output port of the DI box.
• high-impedance instrument level signals from the guitar/bass can be converted to low-impedance microphone level signals. The microphone level signals are ported out through the XLR output (the one with three legs).

Now in my case, I reckon that the DI, if needed, would be the first module on the line: Guitar - DI - Audio interface (a.k.a a soundcard, a focusrite or something similar) - Emulated amplifier. However, most soundcards these days already have built-in instrument level input. So, do I need a DI box? According to this dude, if my Scarlett 2i2 does have a dedicated high-impedance instrument level input, I don’t.