The Audio Interface is the hardware used to connect your computer with the rest of your recording gear.
An audio interface provides you with the ability to use high quality microphones and studio monitors (speakers).
Things to consider while buying an audio interface
1. Number of Inputs/Outputs
2. PC Compatibility
3. Pre-amps Quality
4. Latency level
5. Recording software which comes with the Interface.
My personal choices are as follows.
1. Roland Quad Capture
2. Focusrite 2i2
3. PreSonus Audio Box
4. Steinberg UR22