There are two styles of encryption: deterministic and randomized. Deterministic gets you the same encrypted value every time, while randomized arrives at – at least theoretically – a different value every time (there is no guarantee about global uniqueness or anything like that). Deterministic is best used for columns where you are likely to perform point lookups or seeks, such as LastName perhaps (pseudo-code: WHERE LastName = <encrypt('Smith')>). Randomized is more secure, but should only be used for columns that are display only, such as Salary – I am not going to be looking for all of the people in the Employees table making exactly $84,500 (and if we're encrypting salary, we know we're not going to be performing range queries, either).
The limitations of using "Always Encrypted" feature in SQServerer 2016 is well documented in the below article.