Alfalfa is for young bunnies (under about 6 months) and possibly senior bunnies (over 6 years… but not always necessary for seniors).

Everything else falls into the “grass hay” category and it’s usually personal preference (of the bunny) what types they prefer. Oat can be a little bit fattening, so this is usually fed more as a treat hay. Timothy and Orchard are typically hays that people can feed daily for the bulk of hay consumption. People tend to be allergic to timothy more often, but not have as bad a reaction to orchard, so this is another thing to keep in mind if you have allergies.