kazzawazzawoo
"Gammon" is an English word seemingly derived from the French "Jambon"
I once tried looking at the definitions in a Larousse, and they seem to be the same (basically, cured pork leg meat)
In the UK, "Gammon" is usually used for cheaper cuts, often injected with added salty water and often made up from off-cuts of meat pressed and glued together to look like a joint, and "Ham" is usually used for upmarket or deli versions, or for cheap versions pretending to be upmarket. The overlap is imprecise. I saw some bone-in Gammon joints on sale for the Christmas market that looked like whole hams, and were real meat, intended for a big family meal.
In my experience, London East Enders are more habitual eaters of gammon, and West Enders of ham. The fried gammon steak does not have an upmarket equivalent that I have seen. There are regional differences.
However, a thick slice off a piece of gammon makes a superlative bacon, if fried with eggs and mushrooms, e.g. on Christmas morning or boxing day, and it chunks up well for minestrone, though it emits salty juices which I find are best poured off for disposal.