If i ordered a ARF does that mean it's just the shell i have to assemble and i need to buy a seperate engine and other accessories..or does ARF mean i just need to assemble the whole thing??

ARF means that it's 90% pre-built - all you need to do it the final assembly and add your own Engine and Radio

If you get an arf you will need to purchase a radio system and engine. An arf will come precovered but needs assembly of the major parts using glue and epoxy as well as some basic hobby tools. A rtf will come with the radio and engine needing only a screwdriver and pliers to assemble.