Promotion involves communication techniques aimed at informing, influencing, and persuading customers to buy or use a particular product or service. The promotional mix consists of different promotional methods like advertising, sales promotion, personal selling, public relations, and direct marketing. The optimal promotional mix depends on factors like the product's life cycle stage, nature, competition, and marketing budget. Promotion is effective when it achieves its objectives cost efficiently, and ineffective when objectives are not achieved or achieved at high cost.