Why does the author add ` backtick on the number?

Questions
1

This is from a book

GraphicsGrid[{{g11a, Show[  
  Plot[1.25`-0.5590169943749475` Sqrt[5.`-16.` Re[y]],{y,-3.3, 0.3125}, 
    PlotRange-> All, Ticks->{ {-3, -2, -1},{-3, -2, -1, 1, 2, 3}}],
  Plot[1.25`+0.5590169943749475` Sqrt[5.`-16.` Re[y]],{y,-0.3,0.3125}], 
    AspectRatio-> 1, AxesLabel-> {"\[CapitalDelta]N/\[CapitalDelta]t","N"},
Epilog-> {Circle[{0,0},{0.06, 0.1}], Disk[{0,2.5},{0.06, 0.1}], Arrowheads[0.06],
    Arrow[{{0,3},{0,2.7}}], Arrow[{{0,0},{0,2.2}}], Arrow[{{0,0},{0,-3}}]}]}}]

There are many backticks. Does the author use backticks to reserve the computer space to insure the machine precision for these numbers? What is wrong if he does not use backticks?

Thanks a lot.

2

If you read this

there is a description of what the trailing tick mark means to Mathematica. (And that is completely different from the word “Ticks” in the code above. I’m trying to name what I think you are seeing and get around the posting process mangling the punctuation)