I'll add to this, know how to use good rope, learn a few knots, and you'll be surprised at how often you use them even in your daily life.

My favorites, and thus my recommendations, are these, in order of usefulness.

1. The Bowline. Obviously. It's one of the most versatile knots you can make. You use it to create a loop around something, and that loop will not move. It will not tighten or loosen, it can support your body weight and more. It's often used to haul people up when they've fallen into a crevice or hole, because a noose would tighten around your chest and hurt you on the way up, but a Bowline will not.

And, if you need a noose, you can make a small looped Bowline, and pull the lead line through it to make a noose that will self tighten on whatever your putting it around.

Best of all, the Bowline is easy to remove. You know how hard a regular square knot is to undo? Especially if you've pulled it really tight? A Bowline knot, by design, is always easier to undo, even if it's seen hundreds of pounds of load. It really is the best knot, in my opinion.

If you can only learn one knot, make it a Bowline.

2. Truckers hitch. I use this knot all the time. Have you ever tried to use rope to tie something down? And no matter how tight you pull the rope, by the time you're done making the knot, the rope has slipped a bit, and it's looser than you'd like? Especially annoying when trying to put up a clothes line at camp, and it's all droopy.

Enter the truckers hitch. This knot let's you cinch the rope up super tight, and lock it in place, so it stays that way. Plus the finished knot always has a tail you can pull to easily undo it. This is useful for clotheslines, hammocks, tying stuff to your truck or bike, plenty of uses, easily my second favorite knot. Tied for first, practically.

3. Sheet bend. Have a rope that's too short? Need to extend it a bit to get the job done? Sheet bend, double or triple sheet bend depending on the load. Easily connects two ropes together, and comes undone easy enough when you need it to, unlike if you just used two square knots.

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4. Clove Hitch. Quickly and easily tie the end of a rope to a circular object like a pole or tree. Goes on easy, comes off easy.

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5. Butterfly. Make a non sliding loop anywhere in the middle of a rope. Don't load the rope too hard though, this knot can be tough to undo.

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6. Spike hitch, similar to butterfly, but more likely to slide, tightens like a noose on whatever you loop through it under load, but has a wide variety of uses that become more apparent the more you play with rope and knots. Fun fact, this knot is easy to learn, because it's the basis for the Bowline and truckers hitch.

There's definitely more knots to learn, and others will have opinions on which ones are the best. But these are my favorites. Just learning the first two will be extremely helpful to you.

Edit: wow that formatting really got away from me. I'm on mobile, so I'm leaving it, sorry