Stock options lifecycle

Grant: A contractual promise is made to the employee that S/he will be able to exercise a certain number of shares for a fixed price in the future.
Vesting: The period of time ranging from the moment an employee was granted options, till the time S/he is able to exercise them in total.
Exercise: By the end of the vesting period, holders are able to exercise 100% of their options, at this point of time employees are free to keep or sell their shares.

Grant: A contractual promise is made to the employee that S/he will be able to exercise a certain number of shares for a fixed price in the future.
Vesting: The period of time ranging from the moment an employee was granted options, till the time S/he is able to exercise them in total.
Exercise: By the end of the vesting period, holders are able to exercise 100% of their options, at this point of time employees are free to keep or sell their shares.