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I have been working on high-resolution NIRSPEC data obtained from KECK to calculate radial velocities. I have reduced the spectrum of a target of unknown RV (call the file tar.fits). When I open this target in IRAF using splot, I can use shift+ ( or ) to move through something. Are these orders? apertures? The splot window has the following: [tar.fits[*,27]]: INDEF ap:27 beam 0. Now when using shift + ( or ) the values "27" changes. It ranges from 0 to 84. Is this a multi-dimensional spectrum? If so how do you make it into a 1-D spectrum? I am interested in values of 25,26 and 27. Please let me know! Thanks in advance!

In practice orders and apertures are the same, although sometimes the number of the order has physical meaning (order of dispersion, a gratting property or something like that). What you have is a one-dimensional spectrum because it has already been extracted from a 2d image. I know it's confusing to call it 1d even though there are many orders. But anyway, you can extract a particular order using scopy; for example in your case you could try:
cl>scopy tar.fits tar25.fits aperture=25
This will create a fits file called tar25.fits that contains only the aperture (or order) #25.