You're probably going to receive the same deer in the headlights response at most meat counters here in the U.S., especially if you use terms like "gammon".
Here, the usual terms are "ham", which is the butt joint which can be uncured or cured (usually a salt cure) and smoked or unsmoked. The cheaper ones are water injected to make them more moist. It can be a shoulder cut as well but the expected fare at Easter (and other holidays) is the butt cut since it can be quite large if needed (maybe 10 to 15 pounds).
Then, "bacon", at least here in the U.S., usually is only rib meat that's removed in whole slabs with the skin on and is about 2 inches thick. It's then cured (as above) and most often smoked. For the sliced variety the skin is also removed. It's quite fatty and most people look at the packages closely seeking the one that includes more lean meat. Additionally, the thickness of the slice can vary greatly... usually about 1/8 of an inch and when it gets upwards of over 1/4 inch it's marketed as "thick sliced".
One can buy the bacon in "slabs"... that is with the skin still on and unsliced, but it's still cured and/or smoked. You would cut it away from the skin and slice it yourself.
Finally, one can buy "side pork" which is the same cut as described above, but uncured and unsmoked, usually with the skin still on. It's more common in our Southern States, but can be found elsewhere.
Bacon and side pork of any variety is mostly considered a breakfast meat. Sometimes it's included as a flavoring for side dishes like long or green beans and certainly any dried bean dishes.