"define why individuals are offering goods and services to one another." Because these individuals think it's mutually beneficial to enter into the trade. This

"define why individuals are offering goods and services to one another." Because these individuals think it's mutually beneficial to enter into the trade. This explains all voluntary cooperation including barter and modern trade. I sell my goods and services to someone who needs them because I can then go and buy food with that money. Currency obfuscates this picture a bit but its only role is to solve double coincidence of wants. Underneath it is just barter via a layer of indirection.