For this week's joseki, I thought it'd be good to cover the diagonal after the small knight's approach to the 3-4 point. This is a very popular joseki nowadays and definitely extremely useful to learn.
So typically, in response to black's diagonal, white has a choice of either playing at A,B, or to simply tenuki(this is the most popular)
So black's responses to white's 2 space extension are a diagonal or black extending as well. The kick helps to secure the corner and black's extension helps to leave aji within white's group to be pressured from the lower side.
If white decides to play the three space extension instead, the first result is quite similar with black choosing to extend on the upper side leaving the weakness within white's group untouched. Black's second response is far more active and engages into a battle with white. White actually cannot choose to play the diagonal because white's group is not strong enough for it, so the attachment is needed instead. I won't go into further depth about this, but I will leave a link to the OGS joseki page for you to check out more about this joseki and its variations.
Lastly white can choose to tenuki in this situation and play somewhere bigger. In this case, black has 3 main options. The first is to play the small knight's move over the white stone and the traditional response is the jump at 5 although AI also deems simply extending as playable. Black also has the opportunity to try and seal white in with 4 in the lower diagram. I won't go into depth about this joseki, but it has been played and researched extensively by professionals and has been played many times using AI. Finally, black could just choose to tenuki as well, which is what I like to do within my games, because in most cases, there are many other big spots on the board that are less complicated to play out.
Here is the link to the OGS page: https://online-go.com/joseki/144. I highly recommend that you check it out because this joseki is one of the most important josekis to know nowadays.
I hope you were able to take something away with this post.