Not understanding what happened in this video

I'm not an expert by any means, and it took a while for me to figure out what's happening in this lesson. I'll try to help you out.

The index is used to make sure there are no duplicates of the object. (So you can't follow the user twice, that would not make sense). You wouldn't be able to use the (Unique=True) like how it's used for the username, because you are dealing with 2 attributes tuples.

What goes into the from_user and to_users are Users models from the other table. That is why the ForeignKeyField is used. To allow the storage of User models to form User tuples in the Relationship model

The query methods were harder for me to understand, but I understand it now by thinking of the database like this. These are from_user and to_user examples (each object is divided with |):

from jeeno to kenneth | from kenneth to jeeno | from adam to kenneth | from jeeno to adam | from adam to jeeno

Just to make it clear from jeeno to kenneth means that jeeno is following kenneth ect. Let's use the "def following(self):" query method in this example and the current user will be "Adam". That method returns User.select().join(Relationship, on=Relationship.to_user).where(Relationship.from_user == self). Let's talk about the first part of the code which is User.select().join(Relationship, on=Relationship.to_user) This will retrieve all of the "to_user" data. If we use the data from above. It will look like this:

to kenneth | to jeeno | to kenneth | to adam | to jeeno

It's basically the same as the previous representation but without the "from" attributes mixed in. So now we understand that, let's think about the other half of the code "where(Relationship.from_user == self)". This will further filter the results. Since Adam is the current user (self), the data is then further filtered only showing the to_user data that is from Adam. The data base will now look like this instead:

to kenneth | to jeeno

Using that Query method, now we know all the Users that Adam is following, Kenneth and Jeeno.