[Ethereum] What are artifacts in truffle

The Migrations contract stores (in last_completed_migration) a number that corresponds to the last applied "migration" script, found in the migrations folder. Deploying this Migrations contract is always the first such step anyway. The numbering convention is x_script_name.js, with x starting at 1. Your real-meat contracts would typically come in scripts starting at 2_....

So, as this Migrations contract stores the number of the last deployment script applied, Truffle will not run those scripts again. On the other hand, in the future, your app may need to have a modified, or new, contract deployed. For that to happen, you create a new script with an increased number that describes the steps that need to take place. Then, again, after they have run once, they will not run again.

And yes, the last 2 lines are true Solidity. Look at http://solidity.readthedocs.io/en/latest/contracts.html#creating-contracts inside contract OwnedToken {.

In the folder {project root}/build/contracts/{contract name}.json