Reflexive Java Names?

What is the difference between J2SE Runtime Environment and Java Runtime Environment, SE? Some of my computers have several instances of each in the Add/Remove Programs. I have updated all to J2SE Runtime Environment 5.0 Update 10 and am removing previous updates. I’m not sure what the other is, though, and what to do about it.
For example, there is SE v 1.4.2_03. All of my computers are XP Pro SP2.