Attach is the keyword which we relate to the Equipment, Auras and Fortifications, it's the rules text which manages the functionality of these three types of permanents.

701.3. Attach

• 701.3a. To attach an Aura, Equipment, or Fortification to an object means to take it from where it currently is and put it onto that object. If something is attached to a permanent in play, it's customary to place it so that it's physically touching the permanent. An Aura, Equipment, or Fortification can't be attached to an object it couldn't enchant, equip, or fortify, respectively.
• 701.3b. If an effect tries to attach an Aura, Equipment, or Fortification to the object it's already attached to, the effect does nothing.
• 701.3c. Attaching an Aura, Equipment, or Fortification in play to a different object causes the Aura, Equipment, or Fortification to receive a new timestamp.
• 701.3d. To "unattach" an Equipment from a creature means to move it away from that creature so the Equipment is in play but is not equipping anything. It should no longer be physically touching any creature. If an Aura, Equipment, or Fortification that was attached to something ceases to be attached to it, that counts as "becoming unattached."

Translation:

• 701.3a. - This is the rule that allows the game to move the location of the permanent. And notes that you can't do it if the permanent won't allow it to equip, enchant or fortify.
• 701.3b. - You can't attach to something you're already attached to.
• 701.3c. - The game judges certain things based on when an action was done, and if you attach it to something else and then move it back, you use the new timestamp, not the old one.
• 701.3d. - This is the rules text about unattaching.