Many household projects will require the use of either a voltmeter or ammeter. Knowing the difference between these is important, as different projects will require different testing methods.
An ammeter consists of a short circuit that is between the test points. There is quite a low impedance that goes on with the test points. The reason for this is to keep a drop of current that is on the tested circuit from happening.
There is a high impendence connection that takes place between the test points for a voltmeter. This will in turn cause an open circuit to happen with the test points. This will happen to avoid any voltage drops that will happen on the circuit that is being tested.
Basically, an ammeter is what is used whenever currents need to be measured. It is connected through a series in circuits. Whereas a voltmeter is actually used to measure voltage will connect itself in parallel points in circuits. A voltmeter will create an open circuit where as an ammeter will create a short circuit. These 2 circuits will help you to avoid 2 very different issues.