A vending machine is a machine that dispenses merchandise when a customer deposits coins or bills sufficient to purchase the desired item (as opposed to a shop, where personnel is required for every purchase).
Newspaper vending machine
A newspaper vending machine may open the box with all newspapers after paying for one. It assumes the honesty of the customer not to take more than one, which is helped by the fact that having more is often not useful.
In Japan, with a high population density and low rates of vandalism and petty crime, there seem to be no limits to what is sold by vending machines. One can imagine anything, and it is likely that there is a vending machine available to provide it; even bottles of wine and underwear can be purchased from vending machines.
In the U.S., most vending machines are operated by individuals who buy or rent the machines, stock the merchanise, and keep some of the profits. Other machines, such as U.S. Postal Service machines are maintained by governmental or quasi-governmental entities.
Most modern vending machines have been extensively tested and designed to inhibit theft. Many of these machines are designed essentially as large safes. Every year, a few people are killed when machines topple over on them, either while trying to steal from them, or venting frustration on them, especially when a malfunction causes the machine to fail to dispense the purchased item or the proper change (leading to the humorous saying, "change is inevitable, except from a vending machine").
Soda Pop and Snack machines
The actual causes to vending machine malfunction are usually many-fold. However, certain vending machines use a spiral kind of mechanism to separate and to hold the products. When the machine vends, the spiral turns, thus pushing the product forward and falling down to be vended. If the products and the spiral are misaligned, the spiral may turn but not fully release the product, leaving the spiral snagged on the product and having it hang there. This may cause repercussions to the alignment of the products behind it if someone knocks the hanging product down, as the spiral must move a fixed distance.
Beer & Wine vending machines -- Tokyo