There are many types of tests that can be performed with k6. Each type serves a different purpose.
Each test type is designed to give you different insights about your system.
Smoke Test's role is to verify that your System can handle minimal load, without any problems.
Load Test is primarily concerned with assessing the performance of your system in terms of concurrent users or requests per second.
Soak Test tells you about reliability and performance of your system over the extended period of time.
The important thing to understand is that each test can be performed with the same test script. You can write one script and perform all the above tests with it. The only thing that changes is the test configuration, the logic stays the same.
Different test types will teach you different things about your system and give you the insight needed to understand or optimize performance.
Start with a Smoke test and see how easy it is to get your first load test running!