Default account or main account is the account which executes blockchain transactions if none is provided. Most of the functions have executor in the form of payer | accountCreator | contractExecutor.

Local network

When you are on local network eosio account is preset automatically for you as default/main account. You are able to do

await Account.createFromName('some name')

without the need of specifying the accountCreator every time.

Another network

If you are on another network, you can set the default/main account as follow:

const eoslime = require('jungle').init();
​
const jungleMainAccount = eoslime.Account.load('name', 'privateKey');
eoslime.Provider.defaultAccount = jungleMainAccount;

In this way jungleMainAccount will execute every blockchain transaction whenever the execution account is needed but none was provided.