Can someone explain what is domain and range? Gcse math level please

The domain and range are defined for a relation and they are the sets of all the x-coordinates and all the y-coordinates of ordered pairs respectively. For example, if the relation is, R = {(1, 2), (2, 2), (3, 3), (4, 3)}, then:
Domain = the set of all x-coordinates = {1, 2, 3, 4}
Range = the set of all y-coordinates = {2, 3} take a look at the picture e.g Here, the domain is the set {A,B,C,E}
{
A
,
B
,
C
,
E
}
. D
D
is not in the domain, since the function is not defined for D
D
.

The range is the set {1,3,4}
{
1
,
3
,
4
}
. 2
2
is not in the range, since there is no letter in the domain that gets mapped to 2
2
.