mattmann1972 said:
If you are going to climb you need to learn to climb W/O hooks. A Lanard/flipline/scarestrap

is nessasary to tie in to a tree while you set you new rope position. Keep it simple. Dont get the gear unless you know how to climb W/O them. Learn the basics good saddle, good rope, good instructor!!!!!
What he said. Learn how to climb spikeless first. Work on trimming, then advance to removals.Start with easy trims, on trees with branches all the way to the ground, where you can trim the deadwood out with a handsaw. Stay tied in, learn to tie a good hitch and how to use it.
Once you are confident and trust hanging on your ropes, then move on to the advanced stuff. Get a copy of the Tree Climbers Companion.
To answer your question, a flip line and lanyard are interchangeable, but typically, a flip line has a steel core or is made of thicker, stiffer line. The idea is that its easier to flip up the back side of the tree. Lanyards like this are more common out west where they climb the really big diameter trees.
For the trees most arborists climb, 11 or 12 mm line is most commonly used.
If you spend some time learning a good hitch, you can set up your lanyard exactly the same as your climbing line. The only difference is length and maybe rope color.
A good hitch works much better than any of the mechanical ascenders you see in the catalogs. I like the VT, but there are many others that work well. A search of VT should get some good dialog and pictures.