No Limit is pretty much the complete opposite of Limit poker. While you are very limited about your betting amount in Limit poker you have no restrictions at all in No Limit poker. You can bet all the money you have (buy-in) whenever you want. Of course you have fixed numbers for small blind and big blind. The re-raise in No Limit poker has to be at least twice as much as the previous raise, but of course it can be even higher (or max. all-in). If a player doesn’t have double the amount of the previous raise, but he still wants to re-raise then he has the option of going all-in. This is probably one of the few commonalities between No Limit and Limit poker. Just as with pot limit poker the bet has to be at least as much as the big blind.
Usually this game variant is recommended for more experienced and skilled players. You ask why? Well it should be pretty obvious since here you can lose all your money very fast. That is why I would always recommend new players to start with Limit poker until they have mastered the basics.