salt/hash passwords

[XFSIllusion]

okay, well i've got that far, now answer this question for me....

i register as username 'test', and the pw is 'test' as well. Then I look in the database and get this:
password: 1b413dc15691f817a4891ea48b2c0ef0 salt:%eX

Then I delete the test user, and re-register a user under the SAME user and pw (test). now the database reads...
cdf189fe40f9d20a8194de2a2e74ec02 salt: Y"+

So my question is, why is it different everytime. when i use that line you gave me, it gives the same MD5 encryption but is not calling the salt. is there some function i should be calling in my script, like a salt function? I think the salt field is what causes this, but how does the script know what is in the 'salt' field? should i be calling these varibles with a query or something? this is really getting confusing.