If you mean the classic version and the suvival version, there's a lot of changes compared to classic, such as, but not limited to:

1. You have to find blocks and mine them in order to place them.

2. The addition of crafting tools to mine the rarer blocks and to make digging easier.

3. Enemies now spawn at night to attempt to kill you, but they can be turned off my putting the difficulty to 'Peaceful'

4. A health and armour bar, which decrease via various different means (Falling, drowning, fire and creatures to name a few.)

5. Updates, in which Notch adds new content which isn't in the classic version (Such as the recently released pistons and shears.)

Hope this gave you a fair idea of what the survival version is like! :)