Difference between kleene star and a plus

[bensoa1]

Homework Statement

So this isn't a question from a homework directly, but it's been used in my textbook an I'm not sure of the difference. For example, if I have a^* and a⁺, what is the difference

Homework Equations

The exact wording in the book was {0,1}^* and {0,1}⁺

The Attempt at a Solution

I know the kleene star means you have 0 or more repetitions of that symbol, i.e. 0^* = n occurrences of 0 where n ≥ 0. I'm not sure what the plus means at all

 

[haruspex]

According to http://www.cs.man.ac.uk/~pjj/bnf/bnf.html,

trailing + and * means repeat 1 or more times, or 0 or more times, respectively.​