International marketing is the marketing of goods and services across national borders — selling in, and tailoring to, more than one country. Firms take on the extra cost and complexity of going abroad for several linked reasons:
A larger market. Selling in additional countries dramatically increases the number of potential customers, raising sales revenue and growth beyond what the home market alone can deliver.
Spreading (diversifying) risk. Operating in many markets means a downturn, recession or new regulation in one country is cushioned by sales in others — the firm is less dependent on a single economy.
Extending the product life cycle (PLC). A product that is in decline or maturity at home may be in the growth stage in another country, so entering new markets extends the profitable life of the product (links to 4.5 The product life cycle).
Economies of scale. Selling to more countries increases total output, spreading fixed costs (R&D, machinery, branding) over more units and lowering average cost per unit, which improves competitiveness.
A saturated home market. When the home market is saturated (most potential customers already served, little growth left), international expansion is the natural route to keep growing.
These motives echo 1.6 (why firms become multinational), but here the focus is specifically on the marketing consequences of expanding abroad.