Hi Devika.. :)
That utility function is saying:
Consider two bundles:
A=(1,2) ; B=(1,0)
Out of the two bundles, consumer will first look at the sum.
In this case, sum of quantities in A > Sum of quantities in B.
Therfore, consumer will prefer A to B.
Now, if the Sum is same in both the bundles, then cosumer will look at good2.
eg: A=(1,2) and B= (2,1)
Here, sum is the same. But, A has more good2 than B.
So, A is preferred over B.
:)