Quote Originally Posted by Mick-7
As you suggested, a shift is moving from one position to another without sounding a note.

Slurs and slides are similar but the difference is this: a slur is picking a note and then sliding to another note - without picking the second note.

A slide is picking a note and then sliding up or down through a series of notes, i.e., multiple notes vs a single note note like the slur, and the final note in the series may be picked or not, if it's not picked, it's called a "legato slide."

Here's an essay on slides: Slides Part 1 | StudyBass
This sounds right to me.

The only thing I'd add is that there is a way of doing a kind of quick, partial shift. Your hand moves just enough to make a stretch easier. The hand can shift surprisingly quickly. It's a kind of intermediate solution to the four fingers for five frets problem.