A link is a psychic/energy connection that you have with another person. Every person has created at least one in their life. Most often, the first is with your parents at birth. Any time you create a bond with someone, your forming a link subconsciously. When working with magick, people will often create a link to someone they are focusing on. This gives you a better chance at effecting their energy.
Links have a variety of uses. They aide in healing, readings, spells, or even just knowing how someone is doing. How? When they are created, they give you a direct connection to that person.
Links, no matter how they are created, can have both positive and negative effects on the people that are connected. It does not matter why they were created. They could have been created consciously, or subconsciously for good reasons, and still have ill effects. The opposite is also true. For example, you create a link to a friend that is having mental health issues, and you did not know. You start feeling depressed and less like yourself. That is just a small example of how a link can have adverse effects. Does this mean it is not worth it to be linked to them? No. Regardless of the latter outcome, links are worth creating to give our magick a boost.
Links can be created in a variety of ways. Some people simply think of or focus on the person to create one. Others like to use a picture or special belonging of the persons. By focusing on the person and visualizing a thread connecting you to them, you can create a simple link to them. Some people like to go into creating complex links, just like shields. Obviously, the longer you have had it, and the more work you put into it, the stronger it will be. However, they can all be broken, and/or traced back somehow.
Links cannot be seen physically. To see any links attatched to you, you would need to do an energy scan, or view your aura via astral projection. To know where a link comes from, simply follow it back. If you come across one that seems off or gives you negative feelings, break it. This can be done in any way you wish (sword, scissors, fire etc.). When you break it, make sure to visualize it being completely severed.
For protection purposes, I go through a mental cutting of links every so often. This ensures that there are no links remaining that could cause me or others any form of harm. Since I like to incorporate dance and music into my workings, I will often crank something up on the stereo that is fast paced and resonic. I personally like to burn some sage and cedar while I do this. Standing in the center of the room, take a few deep breaths and hold your arms out parallel with the floor. Using whatever tool you like (whether physical or visualized) swing your arms all around your body. Visualize each link being cut and disappearing. Be creative in your dance. This helps to raise your energy and focus a bit.
Another method I like to use is a mental burning. Rather then using a cutting implement, I visualize a blue-white fire surrounding my body, but not touching it. Not only does it burn up any links connected to you, but it helps to purify the energy surrounding you. When done, you should shield and ground yourself.