Yes, Stereo requires 2 sources.
2mics or 2 line inputs. and eventually 2 ears.

1 mic can only be recorded in mono.
You might also want to look up the word panning.

Enjoy.
thomas Anthony
Manuals can be fun

The issue of recording vocals is a very passionate issue.

Frequently, vocals are recorded as a single, "mono" as in monaural, single channel track. This track is then presented in the stereo mix equally in both of the left & right stereo mix down tracks. With that single channel microphone track, it now appears in the center of the stereo image because within your software mixer or your physical hardware mixer, your local channel "balance" controls better known as a panoramic potentiometer or .pan pot.. It's the same as a balance control since the balance control deals with 2 tracks to begin with. The Panoramic Potentiometer is not a balance control as much as it is a positional control. Especially since you're taking a single mono source and placing it within the left/right stereo image i.e. left, left/Center, Center, right/Center, right. It's the way you build your stereo mix.

You are only hearing your microphone in one ear because the input is passed through to the output. Vocals are not normally recorded in stereo per se as the feeling of stereo space can also be created with external reverb devices or, software-based reverb programs, along with panning your source to center..

Staying in Center ground
Ms. Remy Ann David

Celestine may just be getting the term "stereo" confused with being able to hear from both sides. Celestine may just need to go into the recording software (of what flavor wasn't mention) and configure the track as mono, and assign the input to the input the mic is connected to.

Then, Celestine may be able to hear the signal out both ears, though it will not be stereo.

This is my suspicion.

Otherwise, as mentioned, yes...you need two mics to record stereo.

Kapt.Krunch

What is also not quite being made clear is that when recording "Lead Vocals", the perceptual sound of the lead vocals is that you want them to generally be front and center. If one decides to use a stereo microphone or stereo microphone techniques, any left to right head movements cause the lead vocals to wildly swing left to right in the stereo spectrum. This generally sounds awful and is highly NOT RECOMMENDED.

As to your problem of only hearing the vocal in the left or right earphones is because many sound cards simply pass the input signal to the output. So, yeah, when you are recording a single microphone vocal, your pass through sound may in fact only be heard in a single headphone channel. This however is rectified when played back if your software mixers Panoramic Potentiometers are set to centered "Mono".

Just to be perfectly clear
Ms. Remy Ann David

Hey there,
thanks to you all for your help. It is my suspicion, as the good Kapt. guessed, that I may be mixing up terms here. I am working from very much the ground level up!
I'm really just trying to hear the track on both sides, which I refered to as "stereo," as that has always been my layman association. I'm working with acid, so I'll look around to see if I can change to mono. If anyone knows where to do this in acid, that might well be useful as well:)
Thanks for all of your help in here. My first post- but what a quick and incredible response. Thank God! I'm sure I'll be posting many a more time here. Thanks again.
C