Digital marketing is a bit time taken process to see result while digital advertisement is process to let user know about your products or services directly by banner ads or other advertisement ways to third party websites or portal.
Digital marketing is helpful for long time result means if you got good position in search engines then you will receive lots of traffic and sales for free till your position is good. But with advertisement you will get traffics according to package. For example if you choose advertisement for one month then after one month traffic will be about nothing.