Could you help explain "Subject to"

[Dakota Mivshek]

Hi There,

Question for you all. A house on my street that I really have always liked is currently on zillow under "pre-foreclosure." If I were to approach the owner regarding a sale to me, what are my options here?

If I buy the place "subject to", thus taking over the loan, how does the bank he was using for his mortgage respond? Any initial help surrounding this topic would be helpful - the owner just wants out.