These files let you run geth on your own private chain for contract development. A private chain lets you mine your blocks quickly and easily and you can have all the ether you'll ever need for development.
Edit private_genesis.json as you need, perhaps you'd like to increase the account's funds.
I recommend keeping the difficulty pretty low too, it makes the DAG faster to compute.
When done, run the command from private_geth.ps1. Note that:
- the command there enables ALL management APIs to the RPC which would be a totally unsafe thing to do on the livenet
- you may want to change networkid to a random number
- you may need to change the path to solidity compiler solc (can be downloaded with the cpp-ethereum or eth++ package)
I also provide the private key for the account pre-funded in genesis. The password is abcd.