Trance channeling : This is where the spirit person (often a spirit guide) who is without a physical body swaps places with the medium. The guide can then pass on to those who are listening information about spiritual progression, the spirit world etc. When finished the spirit guide gets out of the physical body and the medium (owner) returns to it.
Inspired writing : This is where the spirit person "inspires" the person who is doing the writing. This can be via pictures but is more often done via speech. This is very much like the situation of someone "taking dictation". Though most mediums will hear the words mentally (inside their head) others hear the speech as though someone physical were standing beside them. In the latter situation anyone in the room at the time will hear what is said.
Automatic writing : In this situation the spirit person actually controls the use of the fingers/hand/arm of the medium. If this is done then the medium can use the "other" hand for something else. He/she usually does not know what is written until he/she reads it after it is finished. Apart from "guidance" either form of writing is useful to get information from spirit people such as past life details etc.