Phone Lines / Routing Etc.

My wife would like to add a separate 'phone line' to our home. I have heard of a set up where up have one phone line/number and when someone calls in there is device with a message to press one number for one phone and a different number for a second phone. To me this sounds simple and likely cost effective for what we want to accomplish. Has anyone heard of this type of setup and what equipment is involved?
Thank you in advance.