In Hinduism, sādhu (skt साधु sādhu, “good; good man, holy man”) denotes an ascetic, wandering monk. Although the vast majority of sādhus are yogīs, not all yogīs are sādhus. The sādhu is solely dedicated to achieving mokṣa (liberation), the fourth and final aśrama (stage of life), through meditation and contemplation of brahman. Sādhus often wear saffron-colored clothing, symbolizing their sanyāsa (renunciation).
This way of life is open to women; the female form of the word is sādhvī साध्वी.
The Sanskrit terms sādhu (“good man”) and sādhvī (“good woman”) refer to renouncers who have chosen to live a life apart from or on the edges of society in order to focus on their own spiritual practice.
The words come from the Sanskrit root sādh, which means “reach one’s goal”, “make straight”, or “gain power over”. The same root is used in the word sādhana, which means “spiritual practice”.
Sadhus are something you see everywhere in India, more or less depending upon whereabouts you are. In Pushkar and Varanasi they are everywhere, standing around early in the morning like angels on a Los Angeles beach.
So, now to some of the different types; We have the Naga Sadhu who wanders from holy place to holy place completely naked and often covered in ash. These guys gather at festivals like the Kumbha Mela, congregating in groups to bond as only naked, ash covered men can.
Then we have the Aghori Sadhu, these guys are very serious, most Indians are a little wary of these guys but they are easy to avoid. They spend their entire lives at the waterfront areas, known as ghats, where the dead bodies are cremated on log fires, they eat from the hollowed out skull of a human corpse and many of their rituals are secret and considered sacrilegious at the same time as being religious, could only happen in India!
Then you just can’t miss the Standing Babas, guys who have vowed never to sit or lie down again, they even sleep standing up!
Then of course wherever you have holy men you also have charlatans, pretend Sadhus to rip off the tourists. We have the same thing in the west as well, religious groups based on profit, the oldest scam in the book and still working a treat.
All things considered India is a pretty cool country to be a wandering monk.