To disable a breakpoint, simply uncheck the checkbox that appears to its left in the list of breakpoints. When a breakpoint is disabled, it is exactly the same as if it had been deleted, except that you can enable it again at a later time, if you choose.
Why would one want to disable breakpoints rather than simply deleting them ?
The first reason is the squirrel instinct; might as well save this in case we ever need it again one day. The other, more important, reason is that you sometimes want a breakpoint to be tested for only after another break point is reached.
Suppose you were looping over all the days of the year and then over all the holidays on that date. If you want to debug a particular holiday on a particular date, you would enable a breakpoint to break on the desired day, and only then enable the breakpoint to stop on a given Holidays Set (otherwise, execution would stop everyday for that Holidays Set).