There are many different types of rope and each type has a purpose. First you need to understand there is natural rope and synthetic rope
Natural rope is made from plant fiber and almost always just twisted together, this is the most common type of rope what most people call “Hemp”. However more likely it is Sasial (light tan color) or Manila (darker brown color). Hemp rope is actually made from the same plant, though different part of the pant, that Marijuana comes from.
Synthetic rope is mostly the nylon and polypropylene ropes. I personally do not like polypropylene that much and have very little of it in my rope box. On the flip side I have a ton of nylon ¼ diamond braid rope which is my preference for teaching knots, tying down tents, tarps, etc.
The size of the material does not matter, even string will fall into natural or synthetic categories. From there of course there are specific types of fibers and weaves. For exampled twisted, braided, diamond braid, etc. Some rope like parachute cord and climbing rope have a diamond braid coating and a core that is just long strains of fiber. Obviously each type of wave and fiber has its pros and cons.
Each type of rope, the fibers its made from, how it is weaved, even how its cared for play a role in how strong the rope is. The packaging of most rope will tell you about the rope, its fibers, what it is load tested for, etc. Also did you know some knots like the Square Knot for example, because of the way they bend the rope actually weaken the rope significantly.
When it comes to lashing always use a natural rope, as synthetic will stretch and over time your lashings will come loose. If you lashed together say a tower, bridge or even a gateway this could become very dangerous if it were to collapse. Could you just picture a 100 foot tower falling apart with a Scout on top, or come crashing down on someones head. One this note, also refer to the Guide to Safe Scouting for example last I checked a monkey/rope bridge had limits on how long it could be, how high off the ground it could be, and not allowed to go across any kind of ditch or ravine.
Rope care is a big issue. If you allow your rope to get dirty for example the dirt will act like sand paper and eat away at the fibers weakening it. Dry rope will also become weak and brittle. The best I found was to keep my rope coiled up in a trunk. I ensure the rope is store coiled and neat, tangled rope will shorten its life span. I then store the trunk in the garage, though some where cooler would be better. (I live in the hot desert so in the summer we often between 107f and 112f.). Occasionally I don go through the rope box and inspect all the rope. I toss way the bad stuff and add in new rope as needed.
Its like anything take care of it and it will take care of you.