What is meant by that an ammeter is always connected in "series"? I came across these words in my textbook:

"The current is measured by an ammeter by connecting it in series in that circuit." 

Can somebody explain to me what does this mean?
(I am just stuck on the word series what does it mean?)
 A: Suppose you have a circuit with some current $I$ flowing in it. Objects in the circuit are in series if all the current $I$ flows through them:

In the top diagram the current $I$ has to flow through $A$ then $B$ so the same current flows through both. $A$ and $B$ are in series.
In the bottom diagram the current $I$ flowing in has to split when it reaches the junction. Some of the current $I_1$ flows through $A$ and some $I_2$ flows through $B$. Then the current recombines and flows out again. So neither $A$ nor $B$ get the full current $I$. $A$ and $B$ are in parallel.
You should now see why the ammeter has to be in series i.e. because we need the full current $I$ to flow through it. If the ammeter was in parallel with some other component then the current the ammeter reads would be less than the true current and you'd get a wrong reading.
A: You want to use an ammeter to measure the current at a particular region in a circuit.
You make a break in the circuit in that region and connect the resulting two ends of the circuit to the two terminals of the ammeter thus again completing the circuit.
This is connecting an ammeter in series as all the current which is flowing in that part of the circuit will now flow through the ammeter.
A: Voltage means Potential difference between two points.
V=IR ( ohms law)
In order to measure the voltage ,voltmeter should be connected in parallel. Voltmeter provides very high resistance .
When voltmeter connected in parallel ..so no current flowing through it due to very high resistance.. Voltage drop will occur..we get some voltage so its indicates voltage ( as per definition).
Now if it is connected in series..then due to high resistance no current will flow through circuit..so no voltage drop occur. Voltage in same line is zero..its indicates zero.So, voltmeter is always connected in parallel.
Current means flow of charge (free electrons) in define direction.
I =Q/t
Current is measured by Ammeter.
Ammeter has very low resistance.
Ammeter is connected in series ..more amount of current flow through it due to low resistance..it act like closed switch..so it indicates the current.
Now, Ammeter is connected in parallel..due to low resistance act like short circuit..chances of ammeter get damaged.
So, Ammeter is always connected on series.
