# 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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