Let us use base-10 for the moment. We know that 265 means 200 + 60 + 5 = 2(10)2 + 6(10)1 + 5(10)0. Then, we can naturally extend this logic to numbers that have a decimal point.
For example, 265.89 means 2(10)2 + 6(10)1 + 5(10)0 + 8(10)−1 + 9(10)−2. because 0.8 is really 8(0.1), and 0.09 is really 9(0.01).
Now, we can apply this representation to binary numbers. We know that 10112 = 1(2)3 + 0(2)2 + 1(2)1 + 1(2)0, then 1011.0112 = 1(2)3 + 0(2)2 + 1(2)1 + 1(2)0 + 0(2)−1 + 1(2)−2 + 1(2)−3 = 8 + 2 + 1 + 0.25 + 0.125 = 11.375. Of course, in this case, the point should be called a “binary point” rather than a “decimal point”.
In summary, the “point” of a number notation is simply a separator to separate the digit for b0 and the digit for b−1, where b is the base of the representation (10 for decimal, 2 for binary, and etc.).