Excellent answers by Elizabeth and the others above. I would add that "RCA" refers to a type of connector (plug and jack), not to the characteristics of the signal that is being sent through the connector. Most turntables in fact connect via RCA connectors, at the far end of a detachable or permanently connected cable. But those RCA connectors must be connected to an external phono stage if one is not included in the preamp (or in the turntable itself in a few cases).
The kinds of signals you are referring to as "RCA" are more properly referred to as "line level," as opposed to "phono level."
Also, it is important that the characteristics of the phono stage be compatible with the kind of cartridge that is being used. Most notably, moving magnet cartridges and low output moving coil cartridges have very different phono stage requirements, although some phono stages provide a choice of settings that allows them to handle either type.