Jogi are the group of who have submitted their entire life worshipping god Shiva. They abandoned their house and wander all around the place taking grains of rice or other cereals and money. They dont work and mostly found in temple area .
Doing yoga to make the god happy and worshipping god is their daily rituals. So, some people also called them as 'yogi' means the people who do yoga everyday.
Most of them wear lungi (a piece of cloth) of yellow of white colour and they walk around with one stick and the bowl so that they can collect grains of rice for the night time. It is believed that they were originated from the hariyana region of India but now a days, they are found in south asian countries in abundant amount. In some holy books of hindu, there is reference of jogi. So we can assume that they were present from the very early period. Since they have to walk all the day to collect food, to protect themselves from sunlight they use powder in their face while the red horizontal line on their head region is tika.