Time borrowed from endpoint:
In a path where the endpoint is a latch device, the borrowing time refers to the time from the clock cycle of the latch that is expended by the previous synchronous device. Or in other words, given that a latch is active during a whole clock pulse, if the path between the previous synchronous device and the latch produce a variation of the capturing data at the latch after the latch is enabled, this will produce a borrowing time from the latch.
For example, in the following two-stage latch base design, the combinational logic block between Latch1 and Latch2 may have more delay than the delay between Latch2 and Latch3. To resolve this discrepancy, the first stage can borrow time from the second clock cycle. In this event, the second clock cycle is left with less time to accommodate the combinational logic block between Latch2 and Latch3
Time given to startpoint:
The above picture shows clearly the meaning of this parameter. It would be the path delay from the synchronous element until the latch