What removing the vig means
Add up the implied probability of every outcome in a market (1 divided by the decimal odds) and the total comes to more than 100%. The extra is the bookmaker's margin, sometimes called the vig or the overround, and it's built into every price you're offered.
Removing it maths out what the bookmaker's own odds say the true, fair probability of each outcome actually is, once its edge is stripped back out.
A worked example
A bookmaker offers 2.05 on one side of a two-way market and 1.85 on the other. Those imply 48.8% and 54.1%, which add up to 102.8%: the extra 2.8% is the bookmaker's margin.
Removing it with Shin's method leaves fair probabilities of about 47.4% and 52.6%, which is fair odds of 2.11 and 1.90. Neither number is what you're offered; both are what the market really thinks is likely.
Shin or proportional?
Proportional spreads the margin evenly across every outcome, in proportion to how likely each one already looks.
Shin assumes part of the margin exists to protect the bookmaker against better-informed bettors picking off long shots, so it shaves slightly less off favourites and slightly more off outsiders. The two methods agree closely on even markets and diverge more on lopsided ones. Sharp Bets uses Shin.
What this isn't
This page shows the fair odds implied by one bookmaker's own market. It doesn't compare that market against Pinnacle or say whether a price elsewhere beats it.
For that, use the EV calculator: it compares a specific price you can get against Pinnacle's line to see if it's actually worth betting.