Corner analysis is analysis of different PVT conditions like slow, fast and typical corners and Scenario analysis or Mode Analysis is Functional mode or Test mode analysis.
Corner as mentioned by dftrtl , is the conditions of PVT on which you test the operation of your chip.
Scenario, is the combination of modes and corners. If you have 2 modes, say func and test and 2 corners, say 1v125C and 0.9v-40C, you will test if the chip works in func mode at both the corners and test mode at both corners, making 4 scenarios. func@1v125C , func@0.9v-40C ...