All additional options can be seen here.
Mute will mute yourself.
Dial can be used to dial additional numbers while on the call.
Hold will place the receiver on hold with light background music.
Blind transfer will allow you to connect this call receiver with another call receiver. It is called blind because it just connects them and leaves you out of the call.
Warm transfer is used to connect the call receiver with another person by first placing the initial receiver on hold, dialing the new receiver, allowing you to speak with the new receiver without the initial receiver, and then merging the calls when ready.