The ZKCross SDK is divided into two parts: the client API for the user interface and interaction, and the Wasm host API for the wasm logic.
The client API is implemented in an authentic web application using e.g. TypeScript with React. It also has the capability to connect to a wallet and deploy wasm images.
On the other hand, the Wasm host API is for the wasm logic which can be written in C/C++/Rust or any other high-level language and compiled into WebAssembly binary code. Wasm host API will export Wasm host functions provided by the runtime, that are exposed to a WebAssembly module so that the module can call them. Wasm host functions provide a way for WebAssembly modules to interact with the host environment, in the case of ZKCross which is the Web3/Blockchain.