sql - select distinct a.* from table query -

i'm on new project , there lot of sql server stored procedures in i'm tasked working on, improving, fixing etc..

i surprised see code this:

select distinct a.*  tbl_applicant 

1. when code work?
2. if did work on tables, masking proper results?
3. what should used instead?

1. if table tbl_applicant exists
2. no, it's eliminate dupliacte rows.
3. select col1,col2 ... tbl_applicant group col1,col2 ... or alias a select a.col1, a.col2 ... tbl_applicant group a.col1,a.col2 ...