Can You Tell Me How Does This Solidity Work?

How does this Solidity work?

I am searching about Solidity and why not ask a question in here?

So what I wonder is: Can we transfer any coin (like Bitcoin, Ripple etc.) in this Solidity or is it special just for Ethereum transactions?

Update: Do I need something like Solidity for DApp in my mobile wallet application that I am currently programming with Flutter or can I just hard-code it?

Solidity is a programming language that compiles in to EVM-compatible bytecode. EVM stands for Ethereum Virtual Machine, but other chains (such as Binance Smart Chain or Tron) have implemented their port of EVM, so it's possible to run Solidity contracts on these networks as well.

Can we transfer any coin (like Bitcoin, Ripple etc.) in this Solidity or is it special just for Ethereum transactions?

Solidity contracts are closed in the chain in which they're running (e.g. Ethereum). It's not possible to perform multi-chain operations only with Solidity. There are tokens such as Wrapped BTC copying the price of the underlying asset (in this case BTC), but they are not able to transfer BTC (on thce of the underlying asset (in this case BTC), but they are not able to transfer BTC (on the BTC chain) using just Solidity.