Bandhan (noun) means a bond, literally
Bandhan (verb) means to tie up
Bandhan in Sahaja Yoga means to "tie up" (Kundalini) or "wind up" vibrations (to get something done).
Here are different types of bandhan we use in Sahaja Yoga.
1. Bandhan we use for meditation, before and after. Watch the following movie where Shri Mataji is explaining how to do it (Excerpt from "To be at Nirvikalpa" talk before Sahasrara Puja 1985):
2. Bandhan we use when we get out of the house for protecting ourselves from sometime not so pure energy that is outside. If we are a parent, we can give bandhan to our little kids as well.
3. Bandhan we give to somebody during workshop. When we work on somebody, we give ourselves a bandhan and so we do for the other person to protect him or her and also ourselves from "catching" from one another.
4. Bandhan we give on the chakras of somebody else. This is a simple circle we draw with the right hand in a clockwise direction (if we work from front) or counter clockwise (if we work from behind)
4. Bandhan we give to our chakras when we perform workshop on ourselves
5. Bandhan when we check our vibrations, i.e. the status of our subtle system. We put our attention in the left hand (that sits still). We can write our name using the right index finger on the left hand. We draw, using the right hand, few circles around the center of the left palm. Then we keep our hands upward and check the sensation in the palms and fingers. Cool is good, hot is less good :)
6. Bandhan that we give when we want to know about a certain item. This can be a person, place, book, movie etc. Similar to the previous one, we just write the name of the item. Cool is good, hot not so much.
7. Bandhan when we want to decide about something. Similar to the previous one, we just write the question
8. Bandhan for getting help in a specific situation.
9. Bandhan that we do for somebody's problems
10. Bandhan when we ask for a certain thing to happen.
Of course, when we want to use the bandhan to decide about some course of action or when we inquire about a person or place, we first have to be in good shape ourselves. That is, when we ask about the status of our subtle system, we should feel cool in all the fingers and above Sahasrara.
We can test ourselves using the Envelope Test: take 5 envelopes, put a photo of Shri Mataji in one. Close the envelopes and try to find in which one is the photo. Repeat the test 5 times. If you find the photo in 100% of the times, then you are good to check vibrations about anything else.