OFS is the term which has gained prominence in the past few months because government as well as private companies are doing it. Full form of OFS is Offer For Sale, it refers to issue of additional stocks by existing listed companies in the market and hence it leads to dilution of promoter’s holdings in the organization.
In offer for sale investors can place orders for buying of shares only and one cannot sell the stock through OFS mechanism, it is different from IPO in the sense than in an IPO companies which are not listed offer their stock while offer for sale is similar to follow on public issue where existing companies offer shares to investors.