regional
Relating to a specific geographic region or characteristic of it.
Auf dem Markt werden viele regionale Produkte angeboten.
Many regional products are offered at the market.

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Relating to a specific geographic region or characteristic of it.
Auf dem Markt werden viele regionale Produkte angeboten.
Many regional products are offered at the market.

The adjective 'regional' derives directly from the noun 'die Region' (the region). It describes everything that belongs to a specific region or is typical of it.
Diese Käsesorte ist eine regionale Spezialität aus dem Allgäu.
This type of cheese is a regional specialty from the Allgäu.
In connection with culture and trade, 'regional' is often used for things that come from a specific area. Typical combinations are 'regionale Produkte' (regional products), 'regionale Küche' (regional cuisine), or 'regionale Traditionen' (regional traditions).
Auf dem Wochenmarkt kaufe ich am liebsten regionale Produkte.
At the weekly market, I prefer to buy regional products.
When 'regional' describes the reach of something, it is limited to a specific area. For example, people speak of 'regionale Nachrichten' (regional news), 'regionaler Nahverkehr' (regional public transport), or 'regionale Unterschiede' (regional differences).
Der Streik betrifft nur den regionalen Zugverkehr.
The strike only affects regional train service.
international
'international' and 'regional' both describe the area something relates to. 'international' goes beyond national borders and concerns several countries or people from different countries. 'regional' stays within a specific area or is typical of that area. So the contrast is: large-scale and across countries versus limited to a region. For companies, events, news, or products, 'international' is appropriate when several countries play a role. 'regional' fits when a specific area is the focus.

Im Supermarkt kauft Lena gern regionales Gemüse aus der Umgebung.
At the supermarket, Lena likes to buy regional vegetables from the surrounding area.
Die Messe ist international, deshalb kommen Gäste aus vielen Ländern.
The trade fair is international, so guests come from many countries.