i want to ask one thing that retainership salary just equal to basic salary or not.?

Answer 1

You asking from a tax perspective right? It is the same but the taxes withheld, if the retainer payment was a large lump sum, is probably greater. You can either claim a larger number of exemptions on your W2 for withholding purposes or let it go and when you file a return at the end of the year, you'll likely get a refund.

Answer 2

Depends entirely on the employer for whom you are working.

Actually, retainership fee (or salary, if you would call it that way) is to ensure that you continue to work for them from time to time. Additional remuneration will depend on your performance in your chosen field. Salesmen usually get a retainership fee plus commission on sales etc. It need not and may not be the basic salary at all.