Southern Baptist Convention
The SBC is not so much a denomination as it is a family of churches who have committed to partner together for the sake of mission. The SBC does not have authority over the local churches who make it up. It is simply a partnership, whereby missionaries can be sent and supported, churches can be planted, ministers can be equipped (in Seminaries), and the gospel can be advanced.
Southern Baptists of Texas Convention
The SBTC is a state convention that essentially partners with churches in TX to help plant churches in TX.
Austin Baptist Association.
The ABA is a local association of Southern Baptist Churches that seeks to help plant and strengthen churches in the Austin-Metro area.