I'm assuming that you have already been charged with a felony, and that you are out of custody during the pendency of your case. I'm also assuming this is an Idaho case.
If you are not already in custody at the time of your plea (in other words out on bond), then the judge will generally allow you to remain out of custody in most cases until a presentence investigation has been completed. You would then come back for sentencing at a later date.
When you come back for sentencing the judge will make a determination of whether you will be sent to prison, jail, or some other penalty. Generally with felonies you will be doing at least some jail time, and not unlikely even prison time.
There is no way for me to give you any indication about what would happen in your case because you have not given nearly enough details to even make an educated guess. If you don't already have an attorney representing you, I would recommend you hire one, and if you cannot afford one, request that the court appoint one for you.
Generally, a new court date will be scheduled for a sentencing hearing. A defendant has the right to have people speak on his or her behalf regarding sentencing.
Whether a person has to go to jail or prison has to do with many factors, including the severity of the offense committed and the circumstances involved. For example, a first-time offender who stole a sucker from a convenience store to rush it outside to a diabetic child in need of sugar will probably not got to jail; but an armed robber with a previous record of violent criminal activity who violently beat a mother in front of her children will likely be going to prison for quite awhile.
On a separate note, it's not a good idea to plead guilty to any crime if you haven's consulted with a criminal defense lawyer. It's even worse when you have not only not consulted with a lawyer, but you also do not have a plea agreement.