It involves a fast 'burst' of ad spend, to drive as many installs as possible in as short a time as possible.
This is because the goal is to get onto a 'top free' or 'top paid' list (for your category or overall) and those are based on a short-term rolling average of units downloaded.
In other words, it's to your advantage to spend your marketing budget all at once, instead of gradually.
Yes, it works, if the budget's high enough and your app's appealing enough for the ad creative to actually drive installs. It can also backfire spectacularly.
