Assertions in selenium can be used in 3 modes which are explained below:

1. assert: If you use assert in your tests then the test will be aborted if the assert fails. Next test case will start executing in case you are running a test suite.

2. verify: If verify is used then the test case will not abort even if the verify fails. It will continue executing and log the failure for the failed conditions.

3. waitFor: waitFor command waits for the condition to become true. If the condition is true already the test case continues else it waits for the conditions to become true. If the condition doesn’t becomes true within specified time-out period test will fail and halt.