What does ta in a business contract stand for?
No yet, but could be. A business proposal is an offer given prior to the actual legal contract that the buyer / seller have agree upon. While the business proposal becomes the framework of the business itself, the legal contract which is a separate written agreement for both enlisting the responsibilities, duties, and scope of both once the business is established.
That would depend on what you contract with your employer binds you to. An employment contract may be a negotiated document and it is therefore not possible to give you a general answer. However, IF your employment contract precludes you from starting another business then YES you would be in breach of contract if you did so.