Tax foreclosure sales| Sheriff's deed without warranty

[Luke H.]

Have a few questions about this statement.  This is in Texas.

Tax foreclosure sales are without warranty of any kind. Purchasers receive a Sheriff's deed that is without warranty. 

Q: What is, and what good is a Sheriff's deed that is without warranty?

Q: If I had this what are my rights for getting someone out of the house? Repairing and renting it out? 
Q: Can the owner come back later and purchase it back?

Any information here would be great!