Brain Computer Interface is a communication system, it communicates between user and computer. Brain Computer Interface (BCI) is used as direct communication with human brain using algorithms'. It's a blessing more for severely disabled people, who are not able to control their body organs, but the mental capacity is normal. Today we live in an era of computer. Any system needs input for processing. Brain generates brain signals called as brain rhythms. Brain rhythms are used as input for BCI system there are mainly five types: delta, theta, alpha, beta and gamma. Brain rhythmic activity is generated when we are in thinking, relax, happy, sad state or when muscular is working, in sleep, deep sleep state. One can capture brain rhythms using two types of techniques: invasive and non-invasive BCI. In invasive BCI electrodes are placed on lobes through surgery, it can harm subjects. Noninvasive BCI uses electrodes placed on scalp for capturing brains signals, it does not harm subjects but signal quality is poor than invasive BCI. Today non-invasive BCI is popular because it is safe for people. Electroencephalography (EEG) is a device which captures brain signals. EEG is non-invasive BC