(x,y) is a pair of real numbers. The meaning is:
(x,y) is an ordered pair of numbers belonging to RRxxRR=RR^2. The first pair memeber belongs to the first set RR and the second belongs to second RR. Althoug in this case is the same set RR. Could be in other cases RRxxZZ or QQxxRR
(x,y) has the meaning of an aplication from RR to RR in which to every element x, the aplication asingns the y element.
(x,y) has the meaning of plane's point coordinates. The first x is the horizontal coodinate (abscisa) and second is the vertical coordinate (ordenate). Both are coordinates.
(x,y) has the meaning of a complex number: x is the real part and y is the imaginary part: x+yi
(x,y) has the meaning of a plane's vector from origin of coordinates
etc...
You will see that meaning of (x,y) could be whatever of above depending of context, but if you think a little bit, all meanings are quite similar
Hope this helps