This is the amount of stock in an initial public offering (IPO) granted by the underwriter to an investor. For most IPOs, the allocation is significantly less than the indication of interest. Investor allocations are often meted out based on commission volume, trading history and type of investor. IPO allocations are normally communicated to investors the morning after the pricing. Large investors typically receive almost all of the allocations of an IPO, and individuals must participate in aftermarket trading.
Trading in the IPO subsequent to its offering is called the aftermarket. Trading volume in IPOs is extremely high on the first day (typically ~70% of the float) due to flipping and aftermarket orders. Trading volume can decline precipitously in the following days.
The price appreciation (or depreciation) in IPOs is measured from the offering price going forward. However, some investors also track returns from the first day close in order to get a better benchmark of IPO performance. While investors often need allocations to capture first-day returns, aftermarket performance is available to anyone.