One of your 3 way switches is wired incorrectly. If you have no electrical background, which by the sounds of it you don't, find someone to fix the wires. I could tell you that one of the travellers and a hot wire have been interchanged, but that doesn't really help you, does it?

There is a defective 3 way switch or like "bigbird 1" said, one of the travelers and the common are interchanged.
If this lighting switch set up was working when you purchased the house, then it is pretty good bet that a switch went bad. If it never worked properly since you have opwned the house, it could be a bad switch or wired wrong.
If you decide to try this repair yourself, be careful because not all manufacturers put the travelers (screws) in the same exact location on the switch. Some will have the travelers on the same side of the switch while others will have them across from each other. The good news is that most will mark on the body of the switch "Common" and that screw will be a different color than the other two.
So look at your old switch and take the wire off the common screw (different color screw) put some tape on it as a marker and install it on the new switch common screw. Then transfer the other two wires. If it was wired correctly and you replaced the defective switch, it should work OK now. If it does not work right, then swap the common with one of the other wires and see if it works now. If it does not work right, then put the wires back the way they were (wire with the tape on the common screw) and add another new 3 way switch at the other end of the hall, using the same process.
With all that being said, if there is more than one wire nut / splice in either of the two switch boxes, don't get involved with it, because you will only be going from bad to worse! Remember this rule of thumb... the first thing to do when you find yourself in a hole... is to stop digging! GOOD LUCK

ok, so buy a new 3 way switch to see if that is problem first. How do I know these current switches are 3 way? Because they both turn on the light?

pull the switches and see how many wires actually connect to them. post what you see here.

one thing i have seen is a HO puts in a second REGULAR switch in series with the first. the system can be turned off by putting either switch in the off position, but BOTH must be on to power the lights. maybe that happened here as well. you would not believe how many homes i have seen this in! and i am not even an electrician, nor do i work on anything other than my own stuff.

You might not need a new switch. It could be that one of the existing ones is wired wrong.
Tell us how the existing ones are conencted. Tell us all the wrie(except grounds) connecton in the switch boxes. Note which wire is connected to the common terminal. The common terminal is either marked COMMON or is theone that is a different colour from theother two. Usually it is the black one.

I suspect it's far more likely it's wired wrong than it's defective.

Pull the switches out at both ends and observe the wiring. The travelers, usually a black and a red will both be in the same romex. The common will be by itself. The 3-way switch will have a dark or bronze screw usually on the lower right hand side of the switch. Right and left is determined by the location of the green ground screw which is on the lower left hand side of the switch. 3-way switches do not have the on/off markings of a regular single-gang switch. The common attaches to that bronze screw. There are two brass screws, one above the common and one on the other side of the switch. The travelers attach to the two brass screws and it doesn't matter in what order. Both 3-way switches need to be wired the same way. It is highly unlikly either switch is bad presuming neither switch is a dimmer.