Yes, there seems to be some ambiguity with DC-DC converter nomenclature. The converters themselves can be called switching regulators or switching converters or just regulators. The terms all address the same thing.
Buck can also be called step-down, but there's other types of DC-DC converters than can step down that are not strictly buck converters. Boost can be called step-up, but again, there are step-up converters that are not classified strictly as boost.
Here's a nice chart that shows all the different types of DC-DC converters.