# Meaning of backtick in conjunction with units [duplicate]

In this fragment from an equation solution the backtick is used twice:

inputs = {HoldForm[
Solve[Quantity[2.2*^12, "Joules"] ==
1/2 (Quantity[68000., "Kilograms"])*v^2, v]],


I thought the backtick was used to make context variables? Is it supposed to be a precision marker or something? Does 2.2` mean "I want the answer only in one decimal place"? I don't understand how/why the backtick is being used here.

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## marked as duplicate by m_goldberg, Artes, Sjoerd C. de Vries, Kuba, ciaoApr 28 '14 at 22:38

This question was marked as an exact duplicate of an existing question.

@m_goldberg I read that post. It does not answer my question. – Tyler Durden Apr 28 '14 at 15:44
Why not? What you show is a number mark. – m_goldberg Apr 28 '14 at 15:45
First of all the question is different (obviously). In the one answer the most relevant thing says "As a number mark to mark the end of an approximate number, and separate the number from its precision value." There are no precision values in the expression above, so I am no closer to understanding why the backtick is being used. – Tyler Durden Apr 28 '14 at 15:48
@m_goldberg probably meant this Q/A... – kglr Apr 28 '14 at 15:55
@kguler. That is a better choice for "duplicate of" than the question I chose. – m_goldberg Apr 28 '14 at 15:58