Yoga means to join. The joining of the soul with the supreme being is called Yoga. According to Shrimadbhagwat Gita 'समत्वं योगः उच्यते' means being free from respect, insult, joy-misery, infatuation and envy etc. is called Yoga.
"योगः कर्मसु कौशलम्" means being expert in deeds is Yoga. Maharshi Patanjai says that 'योगश्चित्तवृत्ति निरोधः' means controlling mind is called Yoga. There are different types of Yogas, such as - Bhaktiyoga, Gyanyoga, Dhyan Yoga, Japyoga, Raj Yoga and Hath Yoga.