Had to laugh. They mean what they say.
Optimise for speed - increases speed
Standard setting - standard profile setting
Optimise for reliability - decreases speed but line more stable
Gaming mode on / off - for gamers
They do indeed mean what they say, but the poster clearly wanted a more technical definition rather than you just changing the order of the words to "explain"...
The OP should also try to set it back to reliability, but even if that resolves the problem it's worth trying a different router as some BeBoxes just don't like fastpath or marginal lines, whereas other routers will often be able to deal with it.
Optimise for speed - lowers target SNR margin, increasing sync speed but possibly making line unstable (losing sync often)
Standard setting - 'medium' target SNR - should be stable on most lines and provide reasonable speeds
Optimise for reliability - Higher target SNR which should make line more stable, lower sync speed.
Gaming mode on / off - Off = Interleave mode (line stability but higher pings) On = fastpath mode (possibly less stable line but lower pings and on good lines, higher sync speed)
Wikipedia has definitions of fastpath, interleave, etc.