Society accepts Alchemy. In fact, they think it is better than the dark, bad shit magic by a long shot. this because of the good it has done in recent years. There are some people here and there who don't like it, thinking it is a craft that perverts natural things by making strange substances or items (like acids), but those people are far and few. 

For Alchemy you can make many different kinds of items (you can always experiment, special materials or herbs you find in travels good for this). You can TRY to make anything, but the DL for certain rare or advanced things (like Liquid Fire (alchemist's fire, but here it is known as Liquid Fire or Sea Flame)) may be alot higher. 

As you travel though you may find scrolls, tomes, or other such writings that depict how to make certain special things, either giving you access to special forms of alchemy or lowering the DL for certain items (like with the Grimoire Trait for instance, it could contain a way to make some special form of item). 

Instant healing potions or shit like that is incredibly rare though, very hard to make even with knowledge (and of course, usually is best for those with a decent Hardiness Score as are all alchemical substances meant to be consumed)

The difference between herbal medicines and alchemical ones is that herbal medicines aren't as strong, but they are somewhat easy to make if you have the appropriate herbs (which means you also don't need to come out of pocket for expensive materials). 

Alchemical medicines or substances meant to be consumed are stronger, but have side affects that occur upon failure of a Hardiness Roll (you still experience the intended affect if you fail the roll, but you also experience the bad side affect). Like a 'healing elixir' would rejuvenate you, healing Energy and Vitality, but upon failure of a Hardiness Roll you become nauseous for a time, getting a -2 to all rolls for about thirty minutes to an hour. Usually Fumbling a Hardiness Roll when drinking things like these means you don't experience the intended affect and you experience the side affect (in some cases, the side affect may be a bit more severe) 

So yea, that's Alchemy and Herb Craft in a nut shell. 

Of course, using Herbs you find in alchemy can not only save you coin on materials, but sometimes can even lower the DL of what you are trying to do (like if you use a potent herb with healing properties or a herb known to be quite poisonous for making poisons)