Update glossary.md

[hyanwong]

Reference ARGs in the glossary when defining a "tree sequence". I hope this clarifies rather than adds to any confusion.

We can address the "what is a tree sequence" stuff in the tutorials too.

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  Coverage   89.76%   89.76%           
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  Branches     5737     5738    +1     
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[gregorgorjanc]

Suggested change

	way to store differences between these trees. Technically, ancestry
	way to store shared branches between these trees. Technically, ancestry

The edge table is storing what is shared, not what is different across local trees. I know this is nitpicking, but thinking in terms of differences I have read in many places really confused me when I started to read about what is tree sequence. The left-right algorithms work with differences, I believe.

[hyanwong]

Hi @gregorgorjanc - I have reworded slightly to take account of your point, and also added a glossary item for position. Could you have a look through the changes and check they now make sense to you? I have also put in some links between the words in the definitions, as I think that is useful.

[gregorgorjanc]

@hyanwong thanks for considering my nitpicking comment;) It reads very clear to me now. I have spotted one typo. Otherwise LGTM!

[hyanwong]

Excellent, thanks for spotting that (and accepted)