Leaking and bleeding are the same thing. Here's video explaining all different ways to switch:
https://www.youtube.com/watch?v=WfCFplQn_vE&t=3s.
When you switch fully, someone else comes to front, and you are pulled or pushed back. When you are co-conscious, you are still fully separate and able to tell who you are and who the other one(s) is/are, and you are able to feel each other's feelings or hear each other's thoughts, able to communicate. You still know who is who, and that there's many of you at the same time.
Bleeding/leaking and blending are situations when it's hard to tell who you are, who else there might be, who is in front most etc. You can be in front, but someone else's thought bleed into you so much you're not sure are you really you anymore, or did you switch, because you know these thoughts are not like yours. Then things are blurry. Someone can ask who you are, but you can't tell for sure. You don't know are you in the middle of switch, if someone is blending with you, which feelings belongs to you and which are someone else's, how many of you there are in front.
Bleeding happens when someone comes near the front and their traits start to leak outside, even if they don't front. Closer they get, more blurry it gets and you can end up being blended. Blending is when there's two or more parts together sharing their traits and there's no clear wall between them, while co-consciousness is when the wall is there and you know to whom all feelings and thoughts belong to or where they come from, although you both can be able to feel them.