Is long term capital gain is taxable after selling of shares

Hello  Experts

I am salaried employee

1. I bought shares before 4 years and sold it now , Is Captical gain is TAXable for these shares If yes then Why it is Taxable because I have heard that shares sold after 1 year or 3 years is not Taxable .

2. If long term captial gain is in minus (-) i mean loss , then will I get some benefit\Expempt  in TAX ?

2. What is Last date of submmiting ITR for salraries employees for finacial year 2016-2017

Thanks