
Certified GKH Gardening Expert
Part or full sun describes the intensity of sunlight that it should receive. Part sun would be the equivalent of a tree canopy being overhead. Light will still penetrate with some spots of sun, where shade is in full shade with no direct sun light, all day.
Full sun will be as it sounds. A plant with a full sun requirement will want no obstruction from the sun while it is up.
Of course, it can and does get much more complicated that that, as some partial sun plants can handle a duration of direct sun but this is not usually more than 4 or 6 hours per day. These plants will need close monitoring to find the balance. You can choose to leave these in dappled sunlight, instead and achieve the same results.
Here is an article that will delve into more detail on the lighting subject: https://www.gardeningknowhow.com/garden-how-to/info/what-is-partial-sunlight.htm