place stitches on waste thread???

[knittingnerd]

Hello,
I am pretty new to the knitting community. I have been teaching myself using youtube or kntting sites like this but I have finally come across something that I can't seem to understand or find. The intructions say:
"at this point I would place all remaining stiches on a waste thread. As you work the fingers, keep the thread in place in case you need to rework any of the fingers"

I have no idea what this means so any help would be wonderful.