In the process of doing research, you are going to end up with a lot of notes, photos. forms and documents. Some of them will be digital, well these days all of them can be digital if you scan them and place them online or at least in your computer program or on Ancestry. However, I am still old fashioned and I keep paper records.
I will tell you that my paper records survived our fire and helped me reconstruct my genealogy when my computer and backup were lost. It makes me a little paranoid. But while this is a valid reason for keeping paper records the main one is much simpler. Portability.
When you are heading to a research facility it is nice to just have your note book with you.
I use a loose leaf with clear plastic sheets and I have one for each of my grandparents. Their ancestors are in their book with copies of pictures and copies of all important document. I put the pedigree chart in the first slot with highlighted areas where I am missing information. So say I am missing the death of a 4th great grandmother you can look at this pedigree chart and at a glace see where I need to be working.
This is just my way of doing things, you can certainly come up with your own. You can of course bring your tablet or computer which I see people doing but for me, I would rather just bring the notebook and not worry about protecting my property. I can't imagine anyone wanting to steal my loose leaf.