Is cetana AKA intention, another word for "karma" or close to it? If not what is it that makes karma different from cetana?
Cetana is the intention that produces the action (karma). In my current understanding, cetana first makes its presence known after the inclusion of sensory perceptions which is interwoven with a feeling tone - either pleasant, unpleasant or neutral - from which one, some, all of these actions occur: more perceptions (thoughts & feelings), speech or physical actions. If we wanted to look at this linearly, cetana occurs right before the karma or action but right after the perceiving. In terms of human perception, centana is largely seen as one element bundled with other important elements often called aggregates in Buddhism.
Therefore, the term 'cetana' is taken quite out of its context. It just means to aim, to have a purpose or a plan, but it is part of a larger chain of events, a chain that binds us to the material world. The key is to see how it functions inside its aggregated ecosystem which is made up of: form, feeling, perception, intention and consciousness. For instance, when forms are perceived through the eye a perception/feeling arises which, in turn, creates a need (cetana) to change that perception using thoughts, speech or actions. The cetana to change what we perceive usually has one of two themes: averting or grasping.
AN 6.63 says kamma is intention.
However it appears intention is at most only mental kamma
Kamma is of three types: bodily, verbal & mental
It is intention that I call deeds. Cetanāhaṃ, bhikkhave, kammaṃ vadāmi.
For after making a choice one acts Cetayitvā kammaṃ karoti—
by way of body, speech and mind. kāyena vācāya manasā.