Walk me through an M&A

In my interview I was asked if I knew what M&A was, and I gave them my answer.

But afterwards they asked me to walk them through an M&A process

I was stumped then because I have always known what M&A was, but not what actually happens in Investment Banks when one occurs, and to the businesses in play.

I told them I didn't know, and they told me if I could walk them through any Financial procedures such as Spin offs, Buy side listings, Divestitures, Underwriting, and raising capital.

Once again I told them what they all meant, but I had no idea how it's done by the Investment Banks.

People who are interested in IBD and finance know the definition of M&A, and other financial services, but how is it actually done? What are the steps that an Investment Bank takes to do any Financial service. Can someone clarify on this?