What is ICO marketing?
You decide to launch an ICO. Then the tokens that you sell have to reach the right audience so you can manage to win the market. Now, how does it reach the right audience? Okay, that is only secondary. How would people know that an ICO is happening on a particular date?
Do you go around telling people individually about such an event? No, hence that work is taken care of by the marketing experts. When you want to reach a wider range of the right audience, you target your advertisements towards them.
For this particular thing to happen, you need the help of an ICO marketing agency or company.