Usually tip-soft and a bit longer, tail-stiff and a bit shorter.
Soft tip allows smoother turn initiation and better dampening.
Stiff tail allows more snap comming out of turn and better ollie power.
Flex pattern varies.
Generally inferior compared to above's "forward" direction.
Some are soft all around enabling forigveness in park.
Some like "Skate Banana" are stiff on the ends and soft in the middle to allow for presses while still being decent at ollying and riding.
In general, if you like speed, go for a directional. If you like tricks, go for a "true" twin.