Many people while starting with Karate automation have this question in mind that what if the difference between Karate and Cucumber.
Infact the only similarity between cucumber and karate is the Gherkin syntax.

karate vs cucumber

Gherkin supports the catch-all symbol ‘*’ – instead of forcing you to use Given, When or Then. This is perfect for those cases where it really doesn’t make sense – for example the Background section or when you use the def or set syntax.Since Karate uses Gherkin, you can also employ data-driven techniques such as expressing data-tables in test scripts.

Coming on the difference , below table summarises the difference between cucumber and Karate

Step Definitions Built-InNo. You need to keep implementing them as your functionality grows. This can get very tedious, especially since for dependency-injection, you are on your own.✅ Yes. No extra Java code needed.
Single Layer of Code To MaintainNo. There are 2 Layers. The Gherkin spec or *.feature files make up one layer, and you will also have the corresponding Java step-definitions.✅ Yes. Only 1 layer of Karate-script (based on Gherkin).
Readable SpecificationYes. Cucumber will read like natural language if you implement the step-definitions right.❌ No. Although Karate is simple, and a true DSL, it is ultimately a mini-programming language. But it is perfect for testing web-services at the level of HTTP requests and responses.
Re-Use Feature FilesNo. Cucumber does not support being able to call (and thus re-use) other *.feature files from a test-script.✅ Yes.
Dynamic Data-Driven TestingNo. Cucumber’s Scenario Outline expects the Examples to contain a fixed set of rows.✅ Yes. Karate’s support for calling other *.feature files allows you to use a JSON array as the data-source and you can use JSON or even CSV directly in a data-driven Scenario Outline.
Parallel ExecutionNo. There are some challenges (especially with reporting) and you can find various discussions and third-party projects on the web that attempt to close this gap: ✅ Yes. Karate runs even Scenario-s in parallel, not just Feature-s.
Run ‘Set-Up’ Routines Only OnceNo. Cucumber has a limitation where Background steps are re-run for every Scenario and worse – even for every Examples row within a Scenario Outline. This has been a highly-requested open issue for a long time.✅ Yes.
Embedded JavaScript EngineNo. And you have to roll your own approach to environment-specific configuration and worry about dependency-injection.✅ Yes. Easily define all environments in a single file and share variables across all scenarios. Full script-ability via JS or Java interop.