A flanger is as an audio process which combines two audio signals. The second signal is slightly delayed and therefore the combined signal produces a “swirling“ effect. In electronic flanging, the amount of delay is varied by a low-frequency oscillator, which causes random “shifts” and “sweeps” in the frequency spectrum of the original signal, thus causing the "flanging" effect.
The name “flanging” came about in the 60s when the effect was derived by having a song recorded on two tape machines while slowing one of the machines down by placing your finger on the tape flange. The effect was used extensively by artist such as The Beatles and Jimi Hendrix. 
- Wet/Dry - the balance between the processed and dry signals
- Delay Time - the delay time of the parallel signal
- LFO Modulation Amount - the amount by which the delay time should be modulated according to the LFO
- LFO Rate - the rate at which the LFO modulates the delay time parameter
- Flanger generally relies on an equal balance of dry and wet signal to achieve the strongest effect, so it is easier when working with plug-ins to adjust the wet/dry balance using the plug-in controls, rather than adding the wet only signal via a send/return loop.. 
- Most of the time, low modulation depths tend to work well for faster LFO speeds (often also referred to as the rate), while deeper modulation works better at slower modulation rates. 
- A flanger can be used to make a mono track stereo by introducing a Haas effect. This technique is useful for 'faking' mono instruments to sound stereo and is widely used in the mixing stages. 
- Subtle flanging can give life to some instruments. For example, flanging a bass can add weight or depth to it. Flanging strings can make them sound thicker without destroying the intonation and tuning of the string ensemble. 
- “Barber Pole” or "Infinite” flanging is a sonic illusion similar to the Shepard tone effect. It is equivalent to an auditory “barber pole” in that the sweep of the flanged sound seems to move in only one direction (“up” or “down”) infinitely, instead of sweeping back-and-forth.