What is "M&A"?

Advising on Mergers & Acquisitions or "M&A" is one of the services that Investment Banks typically offer. They can be on the Sell-side, where they are hired by Company X to help sell the Company X (or a part of it) on behalf of the shareholders or, they can be hired on the "Buy-side" to help advise Company Y on buying another company or division. The almighty motives behind doing M&A: Economies of scale, Increased revenue/Increased Market Share, Cross selling, Synergies, Tax-benefits, Geographical or other diversification.