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From the limited context of the quote, it is referring to this definition of distribution (via Merriam-Webster):
a : the position, arrangement, or frequency of occurrence (as of the members of a group) over an area or throughout a space or unit of time
b biology : the natural geographic range of an organism
Or, if that isn't simple enough, it just means where the members of the species are located. In different contexts it may be simply the range, i.e., the space where any individuals of that species are located, or it might actually refer to the density as well.
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Species distribution is the manner in which a biological taxon is spatially arranged.
In the specific sentence you suggest, it seems that the term species range would have eventually be a little bit more appropriate though. The species range is the delimitation over space where individuals are found. The species range is just the maximum value in every possible direction of your species distribution.
Note however, that we often don't care too much about such semantic details (the sentence sounds correct to me).
Next time, please specify where you get the citation from 1) because context often matter and 2) because it is a copy right issue to not cite your source.
Same as above in simple terms
The term species distribution (and species range) describe the geographical locations of individual of the population (of a species). We are talking about a single species here. The term distribution takes the same definition than it does in statistics if you are used to it.
Imagine you have a population of oak trees. You can position every single individual tree over space Consider the drawing
Each individual is represented by a circle. The blue line represents a river.
Description of the species distribution: There are no individuals south east of the river. There is a clutch of high density at the north west of the study area.
Description of the species range is given by the red circle
The difference between species range and species distribution does not matter much for your purpose. The point is that you understand those terms are concepts describing the geographical locations of individual of the population (or the species if you prefer)