Object: User [TD\username]. CREATE USER [TD\username] FOR LOGIN [TD\usernam] WITH DEFAULT_SCHEMA=[dbo]

I have tried to generate scripts from a database on SQL Server 2008 to a file. When I opened the script file, I saw the following

CREATE USER [TD\MyName] FOR LOGIN [TD\MyName] WITH DEFAULT_SCHEMA=[db_accessadmin]

CREATE USER [TD\Co-workerName] FOR LOGIN [TD\Co_workerName] WITH DEFAULT_SCHEMA=[dbo]

And then other t-sql  statements for creating tables as usual.

My question is why it shows up

1/. not only my name, but also my co-worker name?
2/. for me, DEFAULT_SCHEMA=[db_accessadmin] but for my co-worker, DEFAULT_SCHEMA=[dbo]?

Thank you in advance for your help.