I think you are misunderstanding. Volume Weighted Average Price (VWAP) is both an execution tactic and a benchmark. VWAP as a benchmark simply means the [gross notional traded during the day] / [day volume]. Special trades (derriv tied, as-of, etc) are excluded. VWAP is basically the weighted average trade price of the day that you could have been able to achieve yourself.
Institutional clients will often send their orders to brokers' algos with the instruction to target the VWAP. That just means that the client wants to sort of execute in-line and doesn't have much of a view as far as execution strategy. VWAP as a tactic means that the broker's algo should trade trying to execute percentage-wise the same amount as will trade in the market overall. For example, if you have an order for 1,000,000 shares of XYZ, and on-average 10% of the volume in XYZ trades between 10:30am and 11:30 am, then the algo will execute 100,000 shares in that time period.
Brokers offer many different algos. Some are simple, like TWAP. Time Weighted Average rice. That just means take the number of shares, the time window to execute, and then split it up evenly.
There are all sorts of other algos that do things like trying to minimize impact or take advantage of block liquidity when it becomes available.
On the research side you need to calculate a return series based on something. You could go from open to open, close to close, close to next-day open, etc. Data mining is endless. Another statistic that people use is the VWAP, since its just the average price that traded that day.
There's really no magic to it. It's not that a large volume of trades happen as the price approaches it - it's that by definition the VWAP is the volume-weighted average.
Does that help?