Okay I don't know about the Profit part, but they are needed for Rank Advancement. Below are knots that are rank requirements and videos showing how to tie them. There are also instructions and drawings in the Boy Scout Handbook of course. Unfortunately YouTube is full of poor videos of people tying these knots incorrectly. The below videos are "scoutmaster approved." I have included what Ranks these are needed for but of course they will be useful throughout scouts, and life. (We're not trying to be off the grid "survivalists" but we are trying to learn outdoor skills. This gentleman just happens to be a good teacher and ties the knots correctly.)
Terminology
Most knots are tied toward one end or the other of a section of rope, not right in the middle. So you naturally have a short end of rope on one side of where you're making the knot, and a long part on the other. These are called the Standing Part and the Running End.
Standing End or Standing Part - The long part of the rope.
Running End or Working End - The short part of the rope.
Overhand / Underhand Loop - An Overhand Loop has the Running End going over the Standing Part. An Underhand Loop has the Running End going under the Standing Part. (The Bowline knot is made with an overhand loop. It falls apart if you use an underhand loop.)
Bight - Simply the rope doubled back on itself parallel to make a U. (It's the starting point for the Sheet Bend.) A bight can also be made in the middle of a length of rope.
Tag End - The leftover bit of the Running End sticking out after you're done tying a knot.
For pictures of the above and many more terms, see https://scoutpioneering.com/2013/02/11/knot-tying-terminology/
Square Knot
[Ranks: Scout, Tenderfoot] Used for joining two ropes that are equal in diameter. Skip to 3:30 in this video for the Square Knot. Or watch from the beginning for explanation of the above terms. If the "left over right, right over left" method is confusing, a more visual method is to tie the first half knot, not worrying about or having to remember whether it was left that went over right and what that even means! Then look closely. Loosely lay one running end along its own standing part to form a "bight." Bring the other running end through this loop so that it's also doubling back along its own standing part and "looks right," i.e., not like a granny knot. Tighten it up.
Fun fact: Tying your shoelaces is really just a square knot where you tie the second half of it with two bights making it easy to undo by pulling the tag ends. Mind. Blown.
Two Half-Hitches
[Ranks: Scout, Tenderfoot] Used for tying a rope to a pole or grommet when you don't need it to be adjustable. Don't make the Running End too short, give yourself enough to work with. To tie it correctly, don't reverse the direction the running end wraps around the standing end while tying.
Taut-Line Hitch
[Ranks: Scout, Tenderfoot] Used for tying a rope to a tent stake or second pole to make the length of rope adjustable. (Usually combined with a Two Half Hitch and very useful for guy lines, staking down a tarp, fly or temporary flagpole or making a clothesline. As with Two Half Hitches, the running end wraps around the standing end the same direction each time, just three times around on this one instead of two.
Sheet Bend
[Rank: Second Class] This is related to the square knot but you use it if the two ropes you're tying together are DIFFERENT in diameter. By itself it only stays together under tension so use carefully. The "double sheet bend" shown in the scout book is better. Or add a clove hitch around the bight of the larger rope to make it hold more durably.
Bowline Knot
[Rank: Second Class] (Pronounced "Bo-Lin.") Also known as the Rescue Knot. Use anytime you want a loop that doesn't close down on itself. Practice the method he teaches starting at 5:20 and you can do it with your eye's closed like Mr. Reichert taught Mr. DeLong. Then you're ready to get rescued from a dark cave.
Timber Hitch
[Rank: First Class] Useful for dragging logs or other objects, and used for starting diagonal lashings. (Lashings are also a First Class requirement.)
Clove Hitch
[Rank: First Class] Used as the starting knot for various types of lashings. Also the go-to knot for tying the tent roof to the waist level cross bars at Bartle. No more sagging tent roof!
(You might also notice that the Two Half-Hitches knot is actually the running end making a Clove Hitch around the standing end. So you've known how to tie the Clove Hitch all along!)
Trucker's Hitch
This knot is not a rank requirement, but is used for the Kayaking Merit Badge which requires showing how to secure a kayak to a vehicle or rack using the bowline knot and the trucker's hitch. It's a step up from the taut-line hitch which is prone to slippage. As the name indicates, it's used to tie down loads on a truck bed. Ryan Hoshor says every farmer uses it to tie down hay bales. It's also useful for tarp tie downs and guy lines.