In order to visualise infinity, let us go step by step:
Divide any number say 250 by 50 = 5
Reduce the divisor to 10→25010=25
Reduce divisor to 5→2505=50
Reduce divisor to 1→2501=250
Reduce divisor to 12→2500.5→500
Reduce divisor to 110→250(110)→2500
Reduce dvisior to 11000→250000
Reduce to 11000000000→250000000000
So as you keep reducing divisor you keep getting larger and larger number. Keep reducing divisor to as close to ZERO as possible, you will get VERY LARGE NUMBER. So, finally when you reach ZERO, you expect the result to be so large which you simply describe it as INFINITY.
As someone put it, INFINITY is larger than the largest number you can ever imagine !!!
It is not defined but conceptually understood !!